Who builds this
JoistCalc is built and maintained by Alex — fifteen years in semi and heavy equipment repair, plus a steady run of DIY projects on my own house. That's diesel and hydraulics by trade, not framing and concrete, so every formula here is checked against published construction references rather than my own jobsite experience. What carries over is the habit: a calculator should show its formula so you can verify it yourself, instead of trusting a number on faith.
Why this site exists
Getting a straight material estimate shouldn't require an account, an app download, or wading through a sales pitch for ready-mix delivery. JoistCalc exists to give you a fast, accurate number — cubic yards, tons, board feet, sheets, gallons, or bundles — so you can order the right amount the first time and get back to work.
What you'll find here
Each calculator uses the same industry-standard formulas a foreman or estimator would use by hand, laid out plainly on the page so you can see exactly how the number was reached — not a black box. Every calculator also documents its formula and answers common questions specific to that material, right on the page.
Save, share, and estimate a whole job
Every calculator lets you save a result, copy a shareable link that reproduces it, or print a clean copy. Add saved calculations to a named project on the My Projects page to see a combined material cost and markup estimate for a whole job. Switching the site's language also switches the default measurement system to match — none of this requires an account, and everything is stored only in your browser.
Free, no sign-up, ad-supported
Every calculator is free to use, with no account required. The site is supported by advertising rather than subscriptions or paywalls, which is why you'll see a couple of ad placements on each page — they're kept clear of the calculator forms themselves so they don't get in the way of the tool.
Accuracy first
Formulas are checked against standard industry references for each trade. That said, every result here is an estimate for planning purposes — always confirm final quantities against your project specs, local supplier minimums, and manufacturer coverage rates before ordering material. See the Disclaimer for details.
How each calculator is checked
Showing the formula only helps if the formula is right, and on a jobsite a wrong quantity means a short pour or a second supply run. Every calculator here goes through the same checks before it is published, and again whenever it changes:
- Hand-calculated answers. Every figure in a worked example or reference table is worked out by hand first, then read back off the live calculator. If the two disagree, one of them is wrong, and it gets found before the page goes out.
- Published references, linked. Densities, coverage rates, span limits and code requirements come from the organizations that publish them, including the ICC's International Residential Code, the American Wood Council, the American Concrete Institute, the American Cement Association, NFPA 70, the Gypsum Association and ASTM. Each calculator links them in its "Where these numbers come from" section.
- Every option, not just the default. A value that's right for one material or one sheet size can be quietly wrong for the rest, so every selectable option is checked, not only the one the page opens with.
- Honest labels. When a result is approximate, or when a figure is a regulated claim (insulation R-values fall under the FTC's R-Value Rule), the page says so next to the number.
- Every unit and every language. Each calculator is tested in US and metric units, and switching back and forth must never change a value you typed. Corrections are made in all six languages at once, never in English alone.
Corrections
Mistakes happen, and the honest response is to fix them in the open. In August 2026, while every calculator page was rewritten with worked examples and reference tables, four errors turned up and were fixed: a roofing default that under-ordered shingles by 25%, a drywall screw count that came out a third short on 4×12 sheets, a gravel order volume that left out the waste allowance, and an insulation option that changed nothing. The same review found that some of those fixes had not yet reached the translated pages, and they were corrected in every language. If a result looks wrong to you, send the inputs you used. Reports of a wrong number are dealt with before anything else.
Questions or a calculator request?
Reach out any time — see the Contact page.