WaterCalculator

Water Calculators

Every water calculation in one place — 160 free tools across eight categories, from lab-grade science to the plumbing and bills of an ordinary home. Search for a tool, or browse by category below.

The physics and chemistry of water — density, weight, heat, phase changes, viscosity and humidity.

Flow

25 tools · View category

How water moves through pipes and channels — flow rate, velocity, friction loss and fixtures.

Pressure

15 tools · View category

Water pressure and head — pressure at depth, PSI, head conversions and pressure loss.

Usage

23 tools · View category

How much water a home uses — by fixture, per person, footprints and where to save it.

Cost

13 tools · View category

What that water costs — bills, tiered rates, leak losses and heating costs.

Treatment

22 tools · View category

Making water usable — softening, filtration, reverse osmosis, UV and chemistry.

Pumps

17 tools · View category

Sizing and running pumps — head, horsepower, flow, efficiency and NPSH.

Drainage

16 tools · View category

Moving water away — pipe slope and sizing, sumps, gutters and stormwater.

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Built to be trusted

These aren't thin, single-box widgets. Every calculator is built on the recognised engineering or scientific standard for the quantity — the same formulas professionals use — implemented with exact constants and verified number-by-number against the live tool. Each page shows its working, states its assumptions, and lists its sources.

Our tools are written and reviewed by credentialed water professionals, and each carries the name of the person responsible for it. Read how we build and check them in our methodology, the standards we hold to in our editorial policy, and more on our about page.

John Mac, PE
Science, flow, pressure, pumps, drainage
Sarah Bennett, MS
Treatment, usage, cost