Why is 1 therm = 105,500 kJ, not 100,000?

1 therm is defined as exactly 100,000 BTU. The conversion: 1 BTU ≈ 1,055 joules (by definition), so 100,000 BTU × 1,055 J/BTU = 105,500,000 J = 105,500 kJ. The 'extra' 5,500 reflects the BTU-to-joule ratio.

How do I compare natural gas costs to electricity?

Convert both to kJ. If gas costs $1.00/therm (105,500 kJ) and electricity costs $0.15/kWh (3,600 kJ), then: gas = $0.000009/kJ; electricity = $0.0000417/kJ. Electricity is ~4–5 times more expensive per unit energy, but furnaces are 80–90% efficient while resistance heating is ~100%.

My gas bill shows 50 therms. How many [kWh](/energy/kwh-to-kj/) is that?

50 therms × 105,500 kJ/therm = 5,275,000 kJ. Then 5,275,000 kJ ÷ 3,600 kJ/kWh ≈ 1,465 kWh-equivalent. (Note: actual furnace efficiency is 80–95%, so delivered heating ≈ 1,172–1,392 kWh-equivalent.)

What's the difference between a therm and a BTU?

1 BTU is a tiny unit (roughly the heat to warm 1 pound of water 1°F). 1 therm = 100,000 BTU. Therms are used for billing because they're manageable numbers (homes use 5–100 therms/month); BTU would show as millions and be hard to read.

Therms (US) to Kilojoules (kJ) Converter

Enter a value to instantly convert between energy units.

From

Precision4 dp

1 Therm (US) = 105480.4 Kilojoule

Key Formulas

Kilocalorie → Kilojoule

kJ = kcal × 4.184

Kilojoule → Kilocalorie

kcal = kJ × 0.239006

Kilowatt-Hour → Joule

J = kWh × 3600000

Joule → Kilowatt-Hour

kWh = J × 2.77778e-7

Formula

kJ = thm × 105500

Therms are the US standard for natural gas billing (1 therm = 100,000 BTU), while kilojoules are the international SI energy unit. You need this conversion when translating natural gas consumption into engineering specifications, calculating total energy use for a facility (mixing electricity in kWh and gas in therms), or converting historical thermal data into modern metric standards for regulatory compliance, energy audits, or comparative research.

Source: NIST SP 811, Table B.8

Frequently Asked Questions

Real-World Examples

An energy auditor reviewing a commercial building. 1 therm of natural gas (1 month's base heating) = 105,500 kJ. For annual estimates: 50 therms/winter = 5,275,000 kJ (1,465 kWh-equivalent heating).

1 thm = 105500 kJ

A utility comparing household heating. Customer used 30 therms last month (3,165,000 kJ). At $1.10/therm, that's $33; in kJ terms, it's 3.165 megajoules monthly, clear for energy efficiency tracking.

30 thm = 3165000 kJ

A smart meter analysis. Overnight heating used 0.5 therms (52,750 kJ). At 80% furnace efficiency, actual heat delivered was 42,200 kJ, the rest lost to combustion/ductwork.

0.5 thm = 52750 kJ

A commercial kitchen auditing annual gas usage. 100 therms/month peak (10,550,000 kJ/month) for cooking and water heating. In summer, it drops to 5 therms — a key cost-control opportunity identified by energy modeling.

100 thm = 10550000 kJ

kcal to kj kj to kcal kwh to joules joules to kwh btu to joules calories to joules

Therms (US) to Kilojoules (kJ) Converter

Key Formulas

Formula

Frequently Asked Questions

Real-World Examples

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