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No internet, no account required.
ASHRAE
Validated against the standard.
PDF export
Pro-only. Generate professional reports.
$2.99 Pro
Lifetime unlock. No subscriptions.
How it works
Enter your values
Type in your inputs — the app fills code tables and constants for you, so there's nothing to look up.
Get a code-checked result
Instant answer with a clear PASS / FAIL and the exact ASHRAE reference behind every number.
Save & export
Keep a history of calculations and export a clean PDF report to share or attach to a permit (Pro).
What this calculator does
HVAC work mixes units constantly — BTU/h and tons, CFM and L/s, PSI and kPa, °F and °C. This converter handles the conversions techs reach for every day, so you spend less time doing arithmetic on a tailgate and more time on the job.
Common conversions it covers
- Capacity — BTU/h, tons of refrigeration, kW (1 ton = 12,000 BTU/h ≈ 3.517 kW).
- Airflow — CFM, L/s, m³/h.
- Pressure — PSI, in. w.c., Pa, kPa, in. Hg.
- Temperature — °F, °C, K, plus temperature difference.
Worked example
A 3-ton system = 3 × 12,000 = 36,000 BTU/h ≈ 10.55 kW. Its nominal airflow at 400 CFM/ton = 1,200 CFM ≈ 566 L/s.
Related calculators
Use it alongside the airflow CFM calculator and the heat load calculator.
Unit converter FAQ
What is one ton of refrigeration?
One ton equals 12,000 BTU per hour, roughly 3.517 kW. It comes from the heat needed to melt one ton of ice in 24 hours.
Does it convert pressure units?
Yes, including PSI, inches of water column, inches of mercury, pascals, and kilopascals — the mix HVAC and refrigeration work runs into.
Temperature and temperature difference?
Both. It converts absolute temperatures between Fahrenheit, Celsius, and Kelvin, and handles temperature differences correctly for load math.
Does it work offline?
Yes, it runs 100% offline with no account. Free with rewarded ads; a one-time $2.99 Pro unlock adds PDF export and saved history.
Get Unit Converter on your phone
Free with rewarded ads · $2.99 lifetime Pro · iOS & Android. Works 100% offline on the job site.