Residential gas use
2,500,000 BTU equals 25 therms.
Power conversion
BTU to Therms
Convert BTU to therms at the fixed ratio 1 therm = 100,000 BTU (US therm).
1 BTU1.0000e-5 therm
BTU
Accepts zero, positive values, decimals, and either a dot or comma decimal separator.
1therm
How to convert BTU to therm
Three steps complete the conversion:
01
Take the BTU value
Pull it from the utility bill, annual heating-load estimate, or appliance fuel-input rating.
02
Divide by 100,000
Each 100,000 BTU is one therm. A 36,000 BTU appliance running for one hour uses 0.36 therm.
03
Compare to the utility bill
Therms multiplied by your rate ($/therm) gives the dollar cost of that BTU energy quantity.
Formula
BTU to therm formula
BTU → therm
E(therm) = E(BTU) ÷ 100,000
therm → BTU
E(BTU) = E(therm) × 100,000
Worked example
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.
Start
100,000 BTU
Apply
× 1.0000e-5
Result
≈ 1 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.
British Thermal Units
100,000
BTU
Therms
1
therm
Closest tier:1 therm— = 1 therm
Visual scale
Therms across home gas use
Daily, monthly, and annual gas consumption for a typical residence.
Log scale (×10 between gridlines)
Click any bar to set as reference
Reference: Monthly bill (70 therm). In this therms across home gas use chart, the other bars show the ratio relative to that selected value.
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.
Applications
When to convert BTU to therm
Real-world scenarios where this conversion shows up in engineering, HVAC, and equipment specification work.
Residential gas bills
Match annual heating-load BTU estimates against the therms shown on the utility bill.
Furnace efficiency analysis
Compare AFUE-rated furnace BTU input to actual therms billed to identify oversized or under-performing equipment.
Gas appliance sizing
Convert appliance BTU/hr × hours/day × days/year to therms to estimate yearly gas consumption and cost.
Solar gas-displacement studies
Translate solar thermal hot-water BTU savings to therms-equivalent for utility-bill impact analysis.
Energy audits
Whole-home heat-loss models produce BTU/year results that must convert to therms for client-friendly cost reports.
Guidance
Tips and common pitfalls
Therms ≠ thermal Watts
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.
Watch US vs UK therm definitions
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.
Furnace efficiency reduces useful therms
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
How a therm shows up on your gas bill
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.
Why utilities don't bill in BTU directly
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.
Did you know
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.
Interpretation
How to interpret this result
A U.S. therm is 100,000 BTU and is commonly used on natural-gas bills. Converting the energy quantity does not estimate the volume of gas because heat content per cubic foot varies.
A therm connects natural-gas billing with fuel energy, but cubic feet measure volume. Higher heating value, lower heating value, appliance efficiency, and local gas composition determine how metered volume relates to useful heat delivered.
Examples
Practical calculation scenarios
Energy comparison
1 therm equals 100,000 BTU and approximately 29.307 kWh of energy before appliance efficiency.
Quality check
Mistakes to avoid
- Assuming one therm equals a fixed gas volume everywhere
- Confusing therms with temperature
- Comparing input therms with delivered heat without efficiency
Technical reference: U.S. Energy Information Administration energy-unit definitions.
Scope
Limitations and assumptions
A therm is energy, not a fixed volume of natural gas. Gas composition, billing heat content, appliance efficiency, local correction factors, and utility charges are not derived from the entered BTU value.
Questions
Frequently asked
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Trust and accuracy
Methodology and accuracy
The calculator uses the U.S. therm definition of exactly 100,000 BTU. It scales energy quantities directly without estimating cubic feet, operating cost, or useful delivered heat. The supporting constants and review policy for the therm calculation are documented on our calculator methodology page.
Last reviewed: August 7, 2026
Calculator summary
This converter relates BTU to U.S. therms for energy and billing comparisons. Use the utility’s heat-content and rate data for volume or cost calculations.