Underbidding a job can be a costly mistake for a contractor. When more paint is needed than the original contract specified, it’s the contractor who ends up eating those costs. On the other hand, overbidding a job can result in lost business. Knowing how to accurately estimate the amount of paint for a job is a critical skill for winning bids and making profits.
That being said, making accurate estimates is a skill that comes with experience. Even the most seasoned contractors sometimes need a second opinion since no two jobs are the same. When contractors turn to Access for help determining how much cost to build into a bid to cover the price of paint, we use a basic five-step formula.
Step One: Check the paint manufacturer’s technical data sheet for the number of square feet one gallon will cover. However, this number is unreliable because it is based on the assumption that you are applying only one millimetre of film thickness with 100 per cent transfer efficiency. No matter how carefully your team applies the paint, a 100 per cent transfer rate is impossible. Also, most jobs call for more than 1-millimetre film thickness. So this number is simply a starting point.
Step Two: Determine how many millimetres of film thickness (or paint thickness) you will need to apply. Usually, this is 2 to 3 millimetres, but it always depends on the job.
Step Three: Determine what percentage of transfer efficiency you can expect to achieve. This will depend on your application method. For example, the electrostatic application has a very high rate of efficiency. We figure 80 per cent transfer efficiency can be achieved from the electrostatic application. For conventional air spray systems, the transfer efficiency will be much less. We usually figure about 30 to 40 per cent transfer efficiency for coating applied with a conventional air sprayer.
Step Four: Determine the total square feet of the job. Measure carefully to be sure you get the number right.
Step Five: Now you are ready to use your data to calculate an estimate. Take the number from Step One (the number of square feet 1 gallon will cover according to the manufacturer’s technical data sheet) and divide that number by the number from Step Two (the number of millimetres you will need to achieve the desired thickness). Let’s say your technical data sheet specifies 500 square feet of coverage per gallon and you need to achieve 2-millimetre film thickness.
Your equation will be: 500/2 = 250 square feet per gallon
Next, multiply your new square footage (250) by the number from Step Three (the per cent of transfer efficiency). Let’s say you can expect to achieve 80 per cent transfer efficiency.
Your equation will be: 250 x 0.8 = 200 square feet per gallon
Finally, divide the number from Step Four (number of total square feet for the job) by the square feet per gallon. Let’s say you need to cover 800 square feet.
Your equation will be: 800/200 = 4 gallons of paint
Remember, this is simply an approximate amount. It is always smart to factor in about a 10 per cent cushion to account for errors or waste. Paint estimating is more of an art than a science. Since every job is different, there’s no price that’s exactly right for every job and for every bidder. The best paint estimates are custom made for a particular job.
Once you win a job, be sure you stay on top of your inventory so that you have enough paint when it’s time to execute the project. If it’s needed, do cycle counts to see what you need to order on a regular basis. Part of our job at Access is to know how much product our customers need and how much they have. Our Coating Consultants are in our customer’s warehouses and shops, looking at their inventory so they can avoid any emergencies.
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