About QuantityMath
QuantityMath builds free calculators that answer one question properly: how much material do I actually need?
Every year, home improvement projects waste money in the same two ways. People buy too little material and make a second trip to the store, or they buy too much and end up with half-full cans and opened bags they cannot return. Both problems are arithmetic problems, and arithmetic is free to solve.
How we build our calculators
Each calculator follows the same three principles:
- Measure the real surface. We subtract the areas you are not covering — doors, windows, openings — instead of pretending a room is a solid box.
- Use manufacturer coverage figures. Our default coverage rates come from typical product labels, and we let you adjust them for textured or porous surfaces.
- Always round up. Running out of paint or tile in the middle of a job costs far more than one spare gallon.
How we make money
QuantityMath is free and always will be. It is funded by display advertising and by affiliate links. If you buy a product through a link on this site, we may earn a small commission. This never changes the price you pay and it never changes our calculations — the numbers come from the formulas, not from commercial relationships.
Accuracy and limits
Our calculators are planning tools, not quotes. Real projects vary with surface texture, application method, waste and the person holding the roller. Treat every result as a starting point, and buy a little extra. If you spot an error in a calculation, we want to know about it.
Contact
Questions, corrections or suggestions: hello@quantitymath.com