BTU to Therms
Convert BTU to therms at the fixed ratio 1 therm = 100,000 BTU (US therm).
Interactive
Scale explorer for BTU to therm
Drag the slider or click a tier to see where your BTU value lands on the equipment scale — with live therm output.
Visual scale
Therms across home gas use
Daily, monthly, and annual gas consumption for a typical residence.
Fundamentals
What is BTU to therm?
BTU to Therms converts British Thermal Units to therms by dividing the BTU value by 100,000. 1 US therm equals exactly 100,000 BTU. The formula is E(therm) = E(BTU) ÷ 100,000. The therm is the dominant residential natural-gas billing unit in the U.S. — gas meters measure cubic feet, utilities multiply by the local heating value to get BTU, then divide by 100,000 to get therms for the bill.
A therm is a unit of natural-gas energy equal to 100,000 BTU. It was introduced in the early 20th century to give residential gas customers a convenient billing unit roughly equivalent to the daily gas use of a small home.
Two slightly different definitions exist: US therm (100,000 BTU based on the IT BTU = 105.4804 MJ exact) and EC therm (used in the UK, 100,000 BTU based on the 59°F BTU = 105.506 MJ). The difference is under 0.03%.
Gas utilities calculate therms from the cubic-foot meter reading using a 'BTU factor' specific to each delivery region — typically 1,020-1,050 BTU per cubic foot of natural gas, depending on gas composition.
Formula
BTU to therm formula
Convert 100,000 BTU — exactly one therm — to therms. Useful as the mental anchor: every 100,000 BTU of gas heat = 1 therm on the bill.
How to convert BTU to therm
Three steps complete the conversion:
Pull it from the utility bill, annual heating-load estimate, or appliance fuel-input rating.
Each 100,000 BTU is one therm. A 36,000 BTU appliance running for one hour uses 0.36 therm.
Therms multiplied by your rate ($/therm) gives the dollar cost of that BTU energy quantity.
Applications
When to convert BTU to therm
Real-world scenarios where this conversion shows up in engineering, HVAC, and equipment specification work.
Match annual heating-load BTU estimates against the therms shown on the utility bill.
Compare AFUE-rated furnace BTU input to actual therms billed to identify oversized or under-performing equipment.
Convert appliance BTU/hr × hours/day × days/year to therms to estimate yearly gas consumption and cost.
Translate solar thermal hot-water BTU savings to therms-equivalent for utility-bill impact analysis.
Whole-home heat-loss models produce BTU/year results that must convert to therms for client-friendly cost reports.
Guidance
Tips and common pitfalls
A therm is an energy quantity (100,000 BTU). 'Thermal watts' is colloquial for kW of heat-transfer rate. Different categories — don't confuse them.
The US therm uses the IT BTU; the UK therm uses the 59°F BTU. The two differ by 0.026%. For most billing math the difference is invisible.
1 therm of gas input at 90% AFUE delivers 0.9 therm (90,000 BTU) of useful heat. Always convert at delivered-heat basis for cost comparisons.
Reference
BTU to therm conversion table
| British Thermal Units (BTU) | Therms (therm) |
|---|---|
| 1,000 BTU | 0.01 therm |
| 5,000 BTU | 0.05 therm |
| 10,000 BTU | 0.1 therm |
| 25,000 BTU | 0.25 therm |
| 50,000 BTU | 0.5 therm |
| 100,000 BTU | 1 therm |
| 250,000 BTU | 2.5 therm |
| 500,000 BTU | 5 therm |
| 1,000,000 BTU | 10 therm |
| 2,500,000 BTU | 25 therm |
| 5,000,000 BTU | 50 therm |
| 10,000,000 BTU | 100 therm |
In practice
Industry context and practical notes
A residential gas meter measures cubic feet of gas (or hundred cubic feet — CCF). The utility multiplies the CCF reading by a regional 'BTU factor' (the local heating value) and divides by 100,000 to produce therms. The bill shows therms used and a price per therm. If you used 10 therms at $1.20/therm, that's $12.00. The therm-based system survived since the 1920s because it neatly maps to a small home's monthly heating in single- or double-digit numbers.
A residential gas bill in BTU would read 7,300,000 BTU/month — accurate but unreadable. Cutting six zeros off (using 100,000 BTU = 1 therm) makes it 73 therms. The convenience trumps the SI argument. Some natural-gas-rich states (Texas, Oklahoma) use MCF instead of therms — 1 MCF ≈ 10 therms — but the design principle is identical: pick a unit that puts the monthly bill in the 20-100 range. The therm became dominant simply because the unit fits the typical residential consumption pattern.
The therm was chosen as a billing unit precisely because the typical U.S. residential heating load was around 50-100 therms per month, putting bills in a convenient two- or three-digit range.
Questions
Frequently asked
Related tools
More power converters
Dedicated pages for each conversion pair, with a live calculator, formula, table, and FAQ.
BTU/hr to kW
Convert to kilowatts for metric and European spec sheets.
BTU/hr to MW
Megawatt output for industrial chillers and power plants.
KVA to BTU/hr
Apparent power to heat output, with power factor.
BTU/hr to Horsepower
Thermal power in mechanical hp for motor sizing.
BTU/hr to kcal/hr
Metric calorie-based HVAC spec conversion.
BTU/hr to MBH
Commercial HVAC schedules and boiler plate ratings.
BTU/hr to Tons
Cooling capacity from BTU/hr nameplate to contractor tonnage.
BTU to kWh
Energy quantity for gas-vs-electric cost comparisons.
BTU to Joules
Exact SI energy conversion for physics and chemistry.
BTU to kJ
Engineering and food-science energy in kilojoules.
BTU to MMBTU
Million-BTU for natural gas contracts and trading.
BTU to Therms
100,000-BTU units for residential gas bills.
BTU to Wh
Watt-hours for battery and small-device equivalence.