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Paint Calculator

With our paint calculator you can now calculator how much paint you need for any type of service, room, wall, space in your home.

Paint calculator

Paint calculator instructions

How do I estimate a painting job?

Whether you are planning to paint your home yourself as a DIY project or whether you are intending to hire a professional you will need an understanding of the tasks which go into estimating the amount of paint to use. An estimate or quotation is normally based on the cost of materials and the cost of labour taking into account the different wage grades of the professionals and how many people are required to do the job. As well as the obvious factors just mentioned, you will also have to take into account the cost of specialist tools and equipment that may be required to do the job for example scaffolding, ladders and brushes as well as consumables such as paint solvent, sandpaper and filler. If the contractor intends hiring or buying equipment for this project alone then it is acceptable to charge the total cost to the job whereas if the equipment can be used on more than one job then the costs should be spread over however many projects are involved.

In order to estimate the cost of paint and other supplies you have to work your way through a number of steps to ensure you do not forget anything. Let me tell you the steps and explain each one in turn and later we will talk about a quick calculator to make light work of the calculations.

How to calculate costs

Measure the room. In order to work out how much the painting project will cost you (or how much you can charge someone else) you will firstly need to know the area of the surfaces you intend to paint. This is a relatively simple task, all it needs is the ability to keep track of where you are and not miss anything. The equipment items you need are a retractable tape measure, a pencil and a pad of note paper.

First task is to roughly sketch the outline of the room, one per page. Don’t forget to include all the corners, positions of the doors and positions of each window.

Now move around the room measuring the length of each wall and transferring the measurement onto the paper. Remember that this will be an estimated area so the dimensions do not have to be exact. If necessary you can overestimate the dimensions to the nearest whole number to make the calculations easy.

Next job is to measure the height of the room from ceiling down to the top of the skirting board (baseboard in USA). Once again this measurement is an overestimate.

Subtract the areas not being painted. Measure the width and height of each door and window in the room and transfer these measurements to the drawing as well. Eventually you will be subtracting this area from the total wall area as these will either not be painted at all or will be painted using a different type of paint. Doors will either be painted using undercoat and top coat paint or wood stain and varnish, windows will not be painted where there is glass but will be painted using undercoat and top coat on the wooden window frame and sill. Make a note of which parts are wood, metal or glass. Remember that the glass will not be painted at all!

Calculate how much paint you need. For this you need to have the totals of all the paintable surfaces. Transfer the measurements from the sketch onto a list, keeping the types of paint separate (keep the measurements of the walls separate from the doors and separate from the windows). Don’t forget that you will be painting the plaster surfaces (walls and ceilings) with a water based emulsion paint and usually the ceiling will be a different colour to the walls. The emulsion paint can be ordinary finish or can have a vinyl finish which allows the surface to be washable. Woodwork and metal surfaces will be covered in oil based paint of three different types:

Primer. To adhere to the bare wood surface and give the overlaying paint something to hold on to.

Undercoat. This is a preparatory oil based coat designed to cover the underlying surfaces but allowing the top coat to adhere. Depending on how good the undercoat is at covering you may have to give two coats.

Top coat. This is usually a gloss, silk, satin or matte finish. It is the top coat and provides the hardwearing shell protecting the underlying surface.

Total all the areas depending on the paint type required. You will have to list separately all surfaces requiring :

Emulsion paints (walls and ceilings separately as they may be a different colour). Normally each surface will need two coats.

Primer. Normally only needed if you are painting onto bare wood or metal. One coat only. If the surface has been coated with primer in the past then this stage can be omitted.

Undercoat. This is the paint applied after the surfaces have been sanded down and any holes filled. Usually just one coat is needed but sometimes depending on the colour of the paint and the underlying surface you may need two coats. Choose the colour of undercoat to complement the top coat colour. Usually the topcoat container will advise you on the best undercoat colour to use.

Top coat. Normally just use one coat on metal or wood surfaces. The colour of the top coat will depend on the colour of the undercoat. Look on the topcoat paint container for advice as to which colour undercoat to use.

Read the application instructions on each type of paint. The manufacturer will give advice on what volume of paint will cover a specific area. Don’t forget to make allowances for using more than one coat of paint. If the existing paint is in good condition then two new coats will be enough.

From the measurements you have noted and the manufacturer’s coverage advice you will be able to calculate how many containers of different types of paint you will need to buy.

It is usual practice to overestimate the calculations at each stage and add on 10% of the total volume to allow for variations in thickness of each coat.

Calculate the cost of the paint. Once you have worked out the volume of paint you need, it is time to see what the paint will cost. You already know what type of paint you need and which colour and brand you prefer so it is just a quick job to convert the total paint volume into the standard paint container sizes, whether that is pints, gallons or litres.

Once you have calculated the number of containers required, it is a simple job to multiply the total number of containers of each paint type by the cost per container. This will give you the total cost of each type of paint.

Other materials. Decorating a room is not just about buying paint. You will need to buy accessories to apply the paint and items to prevent the paint from going where it is not needed. The most likely items you will need are:

  • 3” or 4” paint brushes. This is used to apply emulsion paint onto a large area quickly.
  • 2” paint brushes. This is to apply oil based paint quickly on to baseboards (skirting boards in UK). They are also used to accurately ‘cut in’ emulsion paint at the edges of walls so the paint does not overlap onto other surfaces.
  • 1” paint brushes. Used to apply oil based paint onto narrow surfaces such as window frames, door trim (architrave in UK) and other narrow surfaces.
  • ½” paint brush. Used to apply oil based paint onto very narrow surfaces such as window frames.

Paint solvent used to wash oil based paint from brushes and other surfaces. The solvent goes by many names in different countries but they are all the same.

  • White spirit (UK).
  • Mineral spirits (USA & Canada).
  • Mineral turpentine (Australia & New Zealand).
  • Turpentine substitute.
  • Petroleum spirits.

Hand cleaner. You need something other than paint solvent to clean paint from your hands. Although solvent will do the job, it will not help the condition of your skin. Repeated use of paint solvent as a hand cleaner has been shown to cause eczema and other skin problems.

Paint buckets (also known as paint kettles). It is not always convenient to take paint from a heavy paint container such as a 5 Litre or 1 gallon container. Instead transfer a small amount into a smaller bucket so you can carry it easier. There is also less to spill if you knock the bucket over.

Masking tape. This is a self-adhesive paper tape used to cover areas so that paint does not overlap. The adhesive is strong enough to hold the tape in place but weak enough to leave the paintwork undamaged when peeling off.

Masking plastic and masking paper. These are used to cover larger areas when painting using spray guns or if you are a particularly messy brush and roller painter.

Caulking. This is a flexible mastic type material that can be squeezed into cracks before allowing drying and applying paint over the top.

Spray guns. A quick way to apply paint. If you are doing the paint job yourself it may be worth hiring this tool rather than buying one as they can be expensive.

Rollers. A quick and easy way to apply emulsion paint onto walls and ceilings. The main advantage of using a roller is the rapid coverage you can achieve.

Cost of labour. If the painting job is to be a DIY project then the cost of labour will be however much your own time is worth. As you will usually be doing the work in your spare time, the labour cost for this will be negligible.

If you intend hiring a professional then ask for a few estimates from various licensed painting contractors. Usually painters work on their own or with a colleague. Two painters can be expected to cover 2,500 square feet in one to two days (don’t forget to allow time for each coat of paint to dry). Two painters will probably cost about $500 to $600 per day.

Other problems

There are many items not mentioned yet that could lengthen the time to do the job.

Clearing rooms. If you have a lot of furniture to move or cover then the extra time will need to be factored in to your final cost.

Different coloured paints. Waiting for one colour to dry before being able to apply a different colour to an adjoining surface will extend the painting time.

Access. There may be problems with accessing high walls or ceilings. Will you need ladders? Will it be better to pay out for scaffold hire?

Wall repairs. Depending on the condition of the painting surfaces you may need repairs or replacements to be done.

Accidents. Sometimes things don’t always go as planned. Paint may spill and damage carpet or other items of furniture. Expect to pay a little extra on your estimate to account for this. The actual amount will depend on the size of job and ease of access. Although it is an added expense that does not at first sight seem to provide a profit, believe us, personal protective equipment is something that should not be forgotten.

  1. Dust masks when sanding down surfaces.
  2. Protective gloves to prevent skin contact with solvents and paints.
  3. Safety glasses to protect the eyes from solvent splashes.

Access equipment. Always provide adequate access equipment, such as ladders or scaffolding, to make sure that the person doing the work does not have to stretch or lean too much.

Out of all these steps in the cost estimation of a painting project, the most complicated part is the calculation to find out the amount of paint required. Luckily, the calculation has been simplified so all you do is plug the measurements into the app provided and miraculously the volume of paint that is required pops out the other end.

Let us now discuss the painting calculator and how to use it.

How to use our calculator

If mathematics isn’t your thing then why not use our online calculator to work out the approximate amount of paint required to cover the area of your room.

It must be realised that this calculator will only work out the approximate amount of paint as the coverage will ultimately depend on how thickly you apply the paint, how many coats you need to apply to ensure a good coverage and how porous the surface is.

The following are the steps needed to use our paint calculator. The calculator uses metric dimensions (metres and square metres) so if you normally use feet and inches you will have to convert to the correct units.

There are many online metric convertors you can use to do this or you can follow the instructions using the formula below.

1 metre = 1.0936 yards = 3.2808 feet = 39.370 inches

Therefore

Metres = feet X 0.3048

Or

Metres = inch X 39.370

Now that we have sorted that little problem let us get on with talking about the calculator.

CALCULATE. On the opening page of the painting estimator app, click on the CALCULATE box.

AREA OF SURFACE. Enter the number of square metres of the area you want to paint into the box. If you have your measurements in feet and inches then convert this into metres using the formula I showed earlier. Click on NEXT when you are happy with the entry. If you don’t know this area then you can calculate it by clicking on the CALCULATE SURFACE box. This will lead you to another page detailing the breakdown calculation of the paintable surface.

CHOOSE ROOM TYPE. You are given the choice of using a regular four sided room or one with many sides.

FOUR SIDED ROOM. In the TYPE OF SURFACE section you have an option of entering dimensions for

Ceiling. Enter values of width and length. If you wish to enter more than one ceiling then click on the ‘+’ box to open out additional ceiling options. When you have finished entering the values for the ceiling then move on to the next surface choice. If there are no more surfaces to paint then move on to OPENING BY

TYPES.

Walls. Enter values of width and height. If you wish to enter more than one wall then click on the ‘+’ box to open out additional wall options. When you have finished entering the values for the walls then move on to the next surface choice. If there are no more surfaces to paint then move on to OPENING BY TYPES.

Floor. Enter values of width and length. If you wish to enter more than one floor then click on the ‘+’box to open out additional floor options. When you have finished entering the value for the floors then move on to the next surface choice. If there are no more surfaces to paint then move on to OPENING BY TYPES.

Columns. You have a choice of three different column types

Four sided columns. Enter values for width, depth, height and number of columns. If there are no more columns to paint then move on to OPENING BY

TYPES.

Circular columns. Enter values for diameter of the column, height of column and number of columns. If there are no more columns to paint then move on to

OPENING BY TYPES.

Many sided columns. Enter values for perimeter, height and number of columns. If there are no more columns to paint then move on to OPENING BY TYPES.

MANY SIDED ROOM. Enter the perimeter of the room then continue entering the dimensions in the same way as for the FOUR SIDED ROOM.

Ceiling. Enter values of width and length. If you wish to enter more than one ceiling then click on the ‘+’ box to open out additional ceiling options. When you have finished entering the values for the ceiling then move on to the next surface choice. If there are no more surfaces to paint then move on to OPENING BY

TYPES.

Walls. Enter values of width and height. If you wish to enter more than one wall then click on the ‘+’ box to open out additional wall options. When you have finished entering the values for the walls then move on to the next surface choice. If there are no more surfaces to paint then move on to OPENING BY TYPES.

Floor. Enter values of width and length. If you wish to enter more than one floor then click on the ‘+’box to open out additional floor options. When you have finished entering the value for the floors then move on to the next surface choice. If there are no more surfaces to paint then move on to OPENING BY TYPES.

Columns. You have a choice of three different column types

Four sided columns. Enter values for width, depth, height and number of columns. If there are no more columns to paint then move on to OPENING BY TYPES.

Circular columns. Enter values for diameter of the column, height of column and number of columns. If there are no more columns to paint then move on to

OPENING BY TYPES.

Many sided columns. Enter values for perimeter, height and number of columns. If there are no more columns to paint then move on to OPENING BY TYPES.

OPENING BY TYPES. This determines the area which will not be painted such as windows, doors, fireplace and built in cupboards. Enter the values for width, height and number of openings of that size. In order to enter dimensions for other size openings you can click on the box showing the ‘+’ sign for as many extra openings as you need. When you have finished entering dimensions for all the openings, click on the CALCULATE box.

NUMBER OF COATS. Enter the number of coats of paint you think you will require. Press NEXT when you are happy with the entry. If the existing paint is in good condition then you will only require two coats of emulsion paint.

PAINT EFFICIENCY. Choose from one of the options for painting efficiency. Press NEXT when you are happy with the entry.

TYPE OF SURFACE. This section asks for information on the porosity of the surface. All that is required is to highlight the appropriate box. Press NEXT when you are happy with the entry.

MANNER OF PAINT APPLICATION. This asks how the paint will be applied. You have six different application methods. Press GET RESULTS when you are happy with the entry.

AMOUNT OF PAINT REQUIRED. This section will show you the approximate amount of paint you will need based on the values entered on each page.

Why should I use this calculator?

Paint can be very expensive to buy especially if you are using one of good quality. You will need to have an idea of how much paint you must buy when you are at the project planning stage.

When buying paint it is always a good idea to purchase all the paint you need at the same time and from the same production batch. If you don’t buy enough at the start and you find that more paint is required later on, then you will probably be buying paint from another production batch (that means the batch was made on a different day). Sometimes it can happen that a different production batch is made as a slightly different colour. This does not always happen and the company’s quality control system should ensure this doesn’t happen, but are you going to take that chance? By having a rough estimate of the amount of paint required (and looking on the paint container to check on the batch number) you will make sure that you have enough paint for the complete job.

Using the calculator breaks the project down into its component parts and gives you a better idea of the different parts which make up the complete project.

Tips when using the calculator

There are a number of tips you can use to get the most out of the calculator app. Let’s go through them one by one, shall we?

If you possibly can, take your measurements in metric (metres not feet). That way you don’t have to do the extra conversion step.

Always round up your measurements to the nearest metre so you have more chance of having enough paint.

You can use the calculator multiple times to calculate different totals. For example, if you want to calculate the amount of undercoat needed to cover the woodwork, then pretend that the dimensions of the woodwork are the dimensions of the walls and enter these in the wall width and height boxes. You can open out more boxes to accommodate the different types of woodwork such as skirting board (baseboard), architrave (door trim), doors and window frames.

As an example let’s say that the skirting board dimensions along one wall are 3m long and 10cm (0.1m) high. Enter these values into the wall dimension boxes as 3m width and 0.1m height. You now have the area of the skirting board.

If the existing paint coverage is in good condition and is a similar colour then you will probably only need two coats of new paint.

If the new colour is very different from the old colour, for example the old colour was dark and the new colour is light (or vice versa) then it is always worth covering the old paint with white paint first to kill the old colour. White paint is usually cheaper than coloured so the extra coats will cost less and the white will give you a blank ‘canvas’ on which to paint.

Look on the manufacturer’s instructions on the original container for the nominal spreading rate. This will tell you how many square metres can be covered by one litre of paint (or square feet per gallon).

If the room is approximately the same height on each wall, then to save time, measure the horizontal distance all the way around the room (the perimeter) and the height. Either multiply the two together to get the area or if you use the calculator, pretend it is one wall and enter the perimeter as the width.

If the ceiling slopes to provide a triangular wall area, just measure the length of the wall at the base of the triangle and multiply the answer by the height of the triangle. Then divide the result by two. Enter this area into the calculator as a separate wall.

Area of triangle = Length of triangle base X Height of triangle X 0.5

Because the door and its trim (architrave in UK) are both going to be painted with the same type of paint (unless it is a different colour) it is quicker to include the dimensions of the trim in with the dimensions of the door and enter a wider and higher door into the door dimension box.

To conclude

I hope the information you have discovered in this article is useful and easy to understand and the calculator app is easy to use. Painting and decorating your home is not difficult if you are willing to work methodically and carefully and the same is true for calculating the materials you need and their cost.

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