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Measurements & Conversions

Therms to kWh Calculator

Convert gas billed in therms into kilowatt-hours, for comparing gas and electric running costs on the same scale.

  • Answers as you type
  • Every formula cited
  • Calculated in your browser
SettingsSettings for this calculationUS
Market
Imperial · sales tax
The gas quantity in therms, from a bill or a meter reading.

A therm is an energy unit, not a volume, so a bill in therms has already had the calorific value applied to the gas that went through the meter. If what you have is cubic feet or cubic metres off the dial, that is volume and it needs the supplier's calorific value and correction factor before it becomes therms — the figures printed on the bill itself.

Energy

1,465 kWh

High confidence

1 therm = 100,000 BTU = 29.3071 kWh. Exact by definition. Compare fuels on useful heat, which needs each appliance's efficiency as well as this conversion.

Therms entered
50 therms
Kilowatt-hours
1,465.36 kWh
Megajoules
5,275.28 MJ
Then change the inputs to see how far the answer moves.

Show calculation logic

How this was calculated

Formula source(s)

  • 1 therm = 100,000 BTU (IT) by definition; 1 BTU (IT) = 1055.05585262 J (NIST SP 811, Appendix B)
  • NIST SP 811 — 1 kWh = 3.6 MJ exactly

Inputs used

Gas used (therms)
50

Intermediate steps

Therms entered
50 therms
Kilowatt-hours
1,465.36 kWh
Megajoules
5,275.28 MJ
Final result1,465.36 kWh

Confidence note: 1 therm = 100,000 BTU = 29.3071 kWh. Exact by definition. Compare fuels on useful heat, which needs each appliance's efficiency as well as this conversion.

What this calculation does not cover

  • Converts delivered energy, not useful heat. Appliance efficiency sits between the two and this page does not know it.
  • A bill's own kWh figure is derived from metered volume with the supplier's calorific value; where both appear, theirs governs.

Add the equipment this sizes

This result is a specification — 1,465 kWh — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Sources checked 2026-09-12 · v1.0.0

Regulatory standards & verification citations2
  1. 1 therm = 100,000 BTU (IT) by definition; 1 BTU (IT) = 1055.05585262 J (NIST SP 811, Appendix B)
  2. NIST SP 811 — 1 kWh = 3.6 MJ exactly
Cite this page

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Every argument about whether to keep a gas boiler or change the heating runs aground on the units before it reaches the economics. Gas arrives in therms, electricity in kilowatt-hours, and the two are simply not comparable as printed even though both are energy. Putting them on one scale is what this page is for, and the number it gives — 29.3 kWh in a therm — is the one that makes the size of a gas bill legible to anyone used to thinking in electrical units. What it deliberately stops short of is the comparison people want next, because the step after this one needs an efficiency for each appliance, and a condensing boiler and a heat pump differ there by a factor of three in opposite directions.

How to calculate therms to kWh in 2 steps

  1. Gas used (therms)The gas quantity in therms, from a bill or a meter reading.
  2. EnergyThe tool computes the energy from those figures and shows the formula, its sources, and a confidence rating alongside it.

Therms to kWh at common values

Page defaults, not your figures above.

Gas used (therms)Energy (kWh)
5147
10293
20586
501,465
1002,931
2005,861
50014,654

Frequently asked questions

Is a US therm the same as a UK therm?
Yes. Both are defined as 100,000 British thermal units, so both are 29.3071 kWh. What differs between the markets is the unit the bill arrives in — UK gas bills now show kWh, while US bills still commonly show therms or CCF.
What is a CCF and how does it relate?
A CCF is a hundred cubic feet of gas, which is a volume rather than an energy. It happens to be close to one therm because typical pipeline gas carries a little over 1,000 BTU per cubic foot, but the exact relationship is the supplier's stated heat content and it moves month to month.
Can I compare gas and electricity at these numbers?
On delivered energy, yes — that is what the conversion gives you. On useful heat, no, not without the efficiency of each appliance: a 92 per cent condensing boiler turns 29.3 kWh of gas into about 27 kWh of heat, while a heat pump can deliver three times its electrical input. The unit conversion is the start of that comparison and not the whole of it.
Why does my bill's kWh figure not match exactly?
Because suppliers convert from metered volume using a calorific value that varies with the gas delivered, plus a volume correction for temperature and pressure. Their arithmetic starts a step earlier than this page does; where you have both figures on the same bill, theirs is the one to use.
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 — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.