W WhatSize
Standards-reviewed Updated June 2026

Standards-based appliance sizing

Find the right size appliance.
In under 60 seconds.

Stop guessing. Our calculators use official AHAM, DOE, and ACCA standards to recommend the exact size — plus the best model to buy.

Browse calculators Read the guides
Calculators
6
For every major appliance category
Sizing guides
52
By room, by size, by scenario
Updated
June 2026
Refreshed against the latest AHAM, DOE & ACCA publications
Built on AHAM standards DOE appliance data ACCA Manual J principles NEC continuous-load rules

What are you sizing?

Pick a category — most calculators take 30 seconds.

Dehumidifier size calculator

Find the right pint capacity — 500 to 3,000 sq ft

All sizing guides →

Generator size calculator

Portable & standby — check off what you need to power

All sizing guides →

Mini split sizing calculator

BTU recommendations by room type & climate zone

All sizing guides →

Air purifier size calculator

CADR for clean air — bedroom to open floor plan

All sizing guides →

Water heater size calculator

Gallons for your household — tank & tankless

All sizing guides →

Sump pump size calculator

HP for your basement — light to heavy seepage

All sizing guides →

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How it works

Three steps to the right size

1

Pick a calculator

Choose the appliance you're sizing from our category list.

2

Enter your details

Room size, household, climate — a few quick inputs.

3

Get the right size

Exact capacity + top models matched to your inputs.