About

DIY Needs is a free collection of calculators for home improvement and garden projects. Each one answers a single question: how much do I need to buy?

Buying too little means a second trip to the store and mismatched batches. Buying too much wastes money and leaves leftovers in the garage. Our calculators help you get it right the first time, whether you’re painting a bedroom, laying a patio or building a fence.

How we calculate

Every calculator uses standard industry rules of thumb and typical coverage figures published by manufacturers, such as how many square feet a gallon of paint covers or how many bricks fit in a square foot of wall. Each page explains the method in plain language, so you can check the math yourself.

Products vary, so we always recommend checking the coverage printed on the label of the product you’re buying and adjusting the calculator to match.

Our principles

The calculators are free to use, with no sign-up. We don’t collect the measurements you enter, and they never leave your device. We round up so you’re never left short, and we add a sensible allowance for cuts and waste that you can change.

How the site is funded

DIY Needs is supported by affiliate links and, in the future, advertising. When you buy through a link on our site, we may earn a small commission at no extra cost to you. This never changes our calculations. You can read more in our affiliate disclosure.

Get in touch

Spotted a mistake, or want a calculator we don’t have yet? Contact us. We read every message.