Plumbing calculators & guides
Free plumbing tools and plain-English guides for Canada — each gives the answer fast and shows the working behind it.
Water heater size
What size water heater do I need? Pick people + fuel, get the size.
Open tool →First hour rating calculator
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 →Drain slope / fall
Total drop over a run, with the code-minimum slope cited for your area.
Open tool →Tankless water heater size
Flow rate (GPM/Lpm) and temperature rise for an on-demand heater.
In the worksWater softener size
What 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 →Pipe offset calculator
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 →Expansion tank sizing calculator
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 →Sump pump sizing calculator
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 →Pipe volume / capacity
Litres or gallons held in a length of pipe, by diameter.
Open tool →Pipe water velocity
How fast is the water moving in your pipe? Enter the flow rate and inside diameter — get the velocity in ft/s or m/s, checked against the usual design guideline.
Open tool →Pipe friction loss calculator
How much pressure does your pipe run lose to friction? Enter the flow, inside diameter, length and material — get the head loss and pressure drop, using the Hazen-Williams equation.
Open tool →Pipe weight calculator
How much does your pipe weigh? Enter the outside diameter, wall thickness, length and material — get the weight in pounds or kilograms, empty and full of water.
Open tool →Water usage calculator
How much water does your household use? Enter your people, fixtures and habits — get your water use per day, month and year, with a breakdown of where it goes.
Open tool →Pump head calculator
How much head does your pump need? Enter the static lift, the pipe friction loss and any required outlet pressure — get the total dynamic head (TDH) in feet or metres, ready to read off a pump curve.
Open tool →GPM / flow rate
Measure your water flow rate — time a container filling, get gallons per minute.
Open tool →Plumbing unit converter
mm↔inch, bar↔psi, °C↔°F, L/min↔GPM, L↔gal, m²↔ft² — instant, both ways.
Open tool →Drain pipe size (DFU)
Add up fixtures, get the minimum drain pipe size for your code.
In the worksWater heater / repipe cost
Realistic cost range for a replacement or repipe in your area.
In the worksPipe freeze risk
When will your pipes freeze, and what insulation prevents it.
In the worksAbout plumbing calculations
Plumbing work runs on a handful of recurring calculations: how much water a fixture or appliance needs, what volume a run of pipe actually holds, how much slope a horizontal drain needs to carry waste without leaving solids behind, and what size a system component should be for the household it serves. Get these numbers wrong and the symptoms show up later as slow drains, starved fixtures, or equipment that short-cycles — problems that cost far more to fix after the walls are closed.
The calculators here handle the arithmetic part of that work: flow rates, pipe volumes, slopes and sizing. Each one gives the answer first, then shows the working underneath, so you can sanity-check the result instead of trusting a black box. Where a plumbing code rule applies to a calculation, the tool names the code section and edition it used.
Using the results
Treat the results as the starting point for a decision, not the end of one. Plumbing codes differ between countries and are amended locally, so the number that satisfies the national model code may still need adjusting for your municipality. The honest workflow: calculate here, then confirm against the code edition your local authority actually enforces before you cut pipe or pour a slab.
Plumbing guides
- Water heater size guide →
- First hour rating calculator guide →
- Water softener size guide →
- Pipe offset calculator guide →
- Expansion tank sizing calculator guide →
- Sump pump sizing calculator guide →
- Pipe water velocity guide →
- Pipe friction loss calculator guide →
- Pipe weight calculator guide →
- Water usage calculator guide →
- Pump head calculator guide →
- GPM / flow rate guide →
- Plumbing unit converter guide →
- PEX vs copper pipe →