Free calculators and plain-English guides for every trade — plumbing, electrical, HVAC, concrete, framing and more. For tradespeople, contractors, inspectors and homeowners. Every answer shows its working — and names the code section when a rule applies.
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The toolkit
Pick your trade. Each tool asks one clear question, gives the answer, and shows the working behind it. New tools land every day.
What size water heater do I need? Pick people + fuel, get the size.
Open tool →Total drop over a run, with the code-minimum slope cited for your area.
In the worksHow much concrete do I need? Enter length, width and thickness — get cubic yards, metres and bags.
Open tool →How much gravel do I need? Enter length, width and depth — get tons, cubic yards and tonnes for gravel, road base or sand.
Open tool →How much asphalt do I need? Enter length, width and thickness — get the tons (and tonnes) of hot-mix asphalt to order for a driveway, path or car park.
Open tool →How many board feet do you have? Enter thickness, width, length and quantity — get the total board footage of lumber, plus the volume in cubic feet or metres.
Open tool →Enter rise and run — get the pitch (x:12), the roof angle, grade %, slope factor and rafter length.
Open tool →How much roofing do I need? Enter your roof footprint and pitch — get the area, the roofing squares and how many bundles of shingles to order.
Open tool →Enter your floor-to-floor rise — get the number of risers, riser height, run, stringer length and angle.
Open tool →Guides & how-tos
Plain-English answers to what tradespeople, contractors, inspectors and homeowners actually search — each guide cites its sources and links to a free calculator.
Built for the site
The figure you came for is the biggest thing on the screen.
When a code rule applies, the answer names the section and edition — AS-NZS-3500 — so you can verify it. How we calculate →
See the formula with your numbers in it — check it line by line.
Big targets and tabular figures you can read on a dusty phone.
Guidance, not sign-off.These calculators give a fast, transparent indication for typical work. They don't replace a licensed professional — always confirm the final design against the current code adopted by your local Authority Having Jurisdiction (AHJ).