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BTU/hr to kW Calculator

Convert a US BTU per hour rating into kilowatts for sizing metric equipment and electrical supply.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax

Equivalent output

3.52 kW

High confidence

Converted using an exact defined factor of 0.00029307107017222 kW per BTU/hr. This is thermal output, not electrical consumption — do not size a circuit from it.

Conversion factor applied
0 kW per BTU/hr

A contractor working to metric standards who has been handed American equipment specifications needs the reverse journey: a nameplate in BTU per hour, and a heat-loss calculation, supply sizing and paperwork that all expect kilowatts. The conversion is exact, but the number it produces is thermal output and not electrical demand, which is the mistake that matters here. Sizing a supply cable or a breaker from the converted figure will be badly wrong for anything other than direct resistive heating: a heat pump delivering 12,000 BTU/h of cooling draws nothing like 3.5 kW from the wall, and a gas appliance draws almost none at all. Use this figure for heat load and equipment matching, and take the electrical demand from the unit's stated running current instead.

Add the equipment this sizes

This result is a specification — 3.517 kW — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • 1 BTU/h = 0.29307107017222 W (International Table BTU), so 1000 BTU/h = 0.293071 kW

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Frequently asked questions

Can I size the electrical supply from this kW figure?
Only for direct resistive heating, where input and output are effectively the same. For a heat pump or air conditioner the converted figure is heat moved, not electricity consumed, and the running current on the nameplate is typically a third of it or less. For a gas appliance the electrical demand is only the fan and controls. Always size the circuit from the stated running current.
My unit is quoted in tons. How does that relate?
One ton of refrigeration is 12,000 BTU/hr, which is 3.517 kW. The term comes from the rate of cooling produced by melting one short ton of ice in 24 hours. Tonnage is always nominal, so a nameplate 'three ton' unit may test anywhere in a band around 36,000 BTU/hr.
Does this work for heating output as well as cooling?
Yes — BTU per hour is a rate of energy transfer and the conversion is direction-agnostic. Bear in mind that many units carry different heating and cooling ratings, and that heat pump output falls as outdoor temperature drops, so use the rating for the design condition rather than the headline figure.