DIY materials, energy costs, renovation budgets. Skip the lead-gen, skip the signup, get your number in seconds. 100+ calculators for homeowners and DIYers.
10 categories, 100+ calculators. Every answer is instant.
Paint calculator for a 12 x 12 room
"Most home improvement calculators lead somewhere ugly."
A form to "get matched with pros." An email signup. A "quote from a contractor near you" pretending to be a result. A solar calculator that resells your address to 5 installers. We don't. Every calculator here shows the math and gives you the number. No forms. No email. No contractor referral. Just the answer.
A calculator is only as good as the measurements you give it. This guide uses the paint calculator above as the example. The same habits work for concrete, flooring, decking, or any other material estimate.
Take a 14 x 12 ft room with 8 ft ceilings, one door, and two windows. These are assumed sizes, so replace them with your own.
| Step | Calculation | Result |
|---|---|---|
| Wall perimeter | 2 x (14 + 12) | 52 ft |
| Gross wall area | 52 x 8 | 416 sq ft |
| Door (3 x 7 ft) | 3 x 7 | 21 sq ft |
| Two windows (3 x 5 ft each) | 2 x 15 | 30 sq ft |
| Paintable area | 416 - 21 - 30 | 365 sq ft |
| Two coats | 365 x 2 | 730 sq ft |
| Gallons at 350 sq ft per gallon | 730 / 350 | about 2.1 |
That rounds up to 3 gallons. If the walls are textured, add 15%: 730 x 1.15 = 839.5 sq ft, which is about 2.4 gallons. It is still 3 gallons to buy. The calculator uses its own average door and window allowance, so its number may differ a little from this hand check.
Split it into rectangles. Measure the wall length of each section, add the lengths together, and multiply by the ceiling height. An alcove or L-shape is just extra wall.
Slightly too much. A partly used can is easy to store. A second trip mid-project costs time, and a new batch can look a little different.
Yes, as a starting point. Use your own measurements, round up, and check the product label. A contractor or supplier can confirm the final quantities for your specific job.