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 →What is your water heater's First Hour Rating? Enter the tank size, heat input and temperature rise — get the hot water it delivers in the first hour (usable storage + recovery).
Open tool →Total drop over a run, with the code-minimum slope cited for your area.
Open tool →Flow rate (GPM/Lpm) and temperature rise for an on-demand heater.
In the worksWhat size water softener do I need? Enter your household size, water hardness and daily use — get the grain capacity to look for, sized to regenerate about once a week.
Open tool →How long do you cut a pipe offset? Enter the offset and pick the fitting angle — get the travel (the diagonal to cut) and run, with the 45° 1.414 multiplier and rolling offsets built in.
Open tool →What size expansion tank do you need? Enter the water heater or system volume, the temperatures and the fill and relief pressures — get the minimum thermal expansion tank size in gallons or litres.
Open tool →What size sump pump do you need? Do the one-minute pit test — enter the pit diameter and how far the water rises in a minute — and get the gallons-per-hour (or litres-per-hour) capacity your pump must deliver at your lift.
Open tool →How much concrete do I need? Enter length, width and thickness — get cubic yards, metres and bags.
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 — IPC, UPC — 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).