About OneTripDIY

OneTripDIY is a small independent site that works out how much material a home project needs — and, more usefully, how much to actually buy. Bags, sheets, boxes, rolls and boards, not just square feet.

Why the site exists

Almost every material calculator online stops at an area or a volume. "You need 2.3 cubic yards of gravel." That number is useless standing in the aisle, where gravel comes in bags or by the yard, and where getting it wrong means a second trip across town.

Two things follow from that, and they are the whole point of the site:

• Every calculator ends in a purchase count. Bags, boxes, sheets, gallons, rolls — the unit the store actually sells.
• Rooms are not always rectangles. Most calculators make you split an L-shaped room into pieces and add them up on paper. Ours lets you enter each section and does it for you.

Who writes these

The site is written and maintained by The OneTripDIY Team. We are not licensed contractors, engineers or building inspectors, and we do not claim to be. What we do is research each material carefully, take every figure from a published source, and show our working so you can check it.

How the numbers are produced

The short version is below. How we check the numbers sets out the full process — including a mistake the process caught before it reached you.

Every calculator on this site follows the same method:

1. Figures come from published sources. Building code, manufacturer technical data sheets, and recognized industry standards — never from memory or guesswork. The sources used are named at the foot of each calculator page.
2. The arithmetic is shown, not hidden. Each page has a "How this is worked out" section listing every step the calculator runs. If you disagree with a step, you can see exactly which one.
3. Reference tables come from the same formula as the tool. They are generated from it, so the table and the calculator can never disagree — a surprisingly common fault elsewhere.
4. Waste allowances are stated, not baked in silently. You can see the percentage and change it.
5. Every page carries the date it was last checked.

What these calculators are not

They are estimating tools for planning and buying. They are not engineering calculations, they are not a substitute for a professional, and they do not know about your local building code, your soil, your climate or your structure.

Coverage figures vary between products, batches and conditions. Always check the actual packaging before you buy, and check anything structural with your local building department.

Tell us when we are wrong

If a number here looks wrong, we want to know. Every calculator page has a link to report it. We check every report, correct the page, and date the change. That is the only way a site like this stays trustworthy.

Get in touch through the contact page.

How the site is paid for

OneTripDIY is free and carries advertising. Ads never change what a calculator tells you — the arithmetic is the arithmetic. We do not accept payment to recommend a product or a brand.