About
Construction math, done right and given away
FoxCalc is a free library of 17 professional construction calculators covering 10 trades — concrete, framing, decking, fencing, roofing, septic, HVAC and interior finishes. It exists because a second supply run costs more than the material, and because good estimating math should not live behind a paywall.
How the tools are built
Field-standard formulas
Every calculator uses the same math estimators, suppliers and code officials rely on — cubic-yard conversions, pitch factors, riser rules and flow tables — not shortcuts invented for a web page.
Instant and free
No accounts, no paywalls, no usage caps. Results update as you type, and every calculation runs in your browser so your project numbers never touch a server.
Honest about limits
An estimate is a starting point, not a permit. Each page spells out the assumptions behind the math and tells you when to verify against local code or a licensed professional.
What each calculator includes
- The exact formula used, written out so you can check the math yourself.
- Worked examples with real dimensions and real results.
- Reference tables — bag yields, pitch multipliers, tank sizes — you can use without the calculator.
- Common mistakes and pro tips gathered from how the work actually goes wrong on site.
- Imperial and metric units, shareable result links, and a printable estimate sheet.
A note on accuracy
FoxCalc estimates are planning figures. Soil conditions, local building codes, product specifications and site access all change real-world quantities and costs. Always confirm structural requirements with your local building department and final pricing with your suppliers before ordering materials or signing a contract.