Global HVAC calculators • Imperial & Metric

Free HVAC Calculators — Instant, Accurate Results

Professional-grade heating and cooling calculations for homeowners and tradespeople worldwide. Imperial & Metric support.

Imperial & Metric

Units that match your job

Fast & mobile-first

Designed for on-site use

Practical outputs

Clear sizing guidance

Popular calculators

Pick a tool and get results in minutes—ideal for quick estimates, planning, and real-world sizing decisions.

Estimate cooling and heating load based on room size, insulation, and usage.

Size a boiler for efficient comfort with clear outputs for kW and BTU/hr.

Get a practical starting point for heat pump sizing with climate-aware inputs.

Looking for sizing guides?

Browse our step-by-step guides for boilers, heat pumps, and cooling—plus links to the free calculators.

Clean inputs, consistent units, and outputs you can explain to a customer or use for planning—without the noise.

Clear assumptions and practical sizing ranges for quick decision-making.

Switch units seamlessly so your results match local standards and equipment.

A streamlined interface that’s easy to use on-site, in a van, or at home.