Megajoules to BTU Converter
Common Conversions
| MJ | BTU |
|---|---|
| 0.001 | 0.948 |
| 0.01 | 9.478 |
| 0.1 | 94.782 |
| 0.5 | 473.909 |
| 1 | 947.817 |
| 1.05506 | 1000 |
| 5 | 4739.09 |
| 10 | 9478.17 |
| 50 | 47390.9 |
| 100 | 94781.7 |
| 500 | 473909 |
| 1000 | 947817 |
Why this conversion matters in chemistry
Cross-market natural-gas pricing is where this conversion shows up. ISO 6976 reports natural-gas heating value in MJ/m³ at 15 °C, 101.325 kPa — about 38.7 MJ/m³ for pipeline gas. The US convention is BTU/scf at 60 °F, 14.696 psia — about 1039 BTU/scf for the same gas. The ratio of 947.817 BTU per MJ comes from 1 BTU = 1.05506 kJ. The small reference-state mismatch between 60 °F and 15 °C produces about a 0.5% residual that a rigorous Wobbe-index analysis accounts for explicitly. Worth doing carefully when SI gas-calorimetry data ends up reported in the BTU form a US heating-value contract or trading desk uses.
Formula
Where the factor comes from
Both ends of this pair are defined rather than measured, but only one of them is tidy. The megajoule needs no unpacking: 10⁶ coherent SI joules, with no uncertainty anywhere on that side. The international-table BTU is assembled from three exact pieces of its own — the avoirdupois pound at 453.59237 g, the Fahrenheit degree at 5/9 of a kelvin, and a specific heat of one IT calorie per gram-kelvin, that calorie being exactly 4.1868 J. Multiplied out they give 1055.05585262 J. Inverting for a per-megajoule factor gives 10⁶ ÷ 1055.05585262 = 947.8171203…, a ratio of exact numbers that never terminates — so a printed 947.817 is a rounding of an exact quantity, not an estimate of a measured one. Swap in the 4.184 J thermochemical calorie and the same factor lands at 948.451.
Precision and significant figures
You can print as many digits of the factor as you like, and almost none of them survive contact with the input. A bomb-calorimeter heat of combustion reproducing to a couple of tenths of a percent supports three significant figures, four at a stretch; a burner nameplate rounded to the nearest thousand BTU/hr supports two. Truncating the factor to 947.8 shifts a 1000 MJ total by roughly 17 BTU out of 947,817, about two parts in 100,000, which nothing in this measurement range will register. Use 947.82 for hand arithmetic, park the full value in a spreadsheet cell where extra digits cost nothing, and set the reported figure count from the calorimetry rather than from the constant.
Worked Examples
The conversion anchor — one megajoule in BTU.
Exactly 1000 BTU — useful as the reverse-anchor scale check.
10 MJ — about a small heating-system hourly fuel-value figure.
100 MJ — about a US therm of natural-gas heating value.
Common mistakes
Which BTU the document meant
A figure labeled only "BTU" may be international-table or thermochemical, and the two per-megajoule factors — 947.817 against 948.451 — differ by about 0.067%. On one conversion that is invisible. Totaled across a fuel inventory or carried into an energy balance that has to close, it becomes a residual with no physical cause, and chasing it wastes an afternoon.
MJ/kg is not BTU/lb
Fuel energy densities carry a mass in the denominator that the energy factor does not touch. Multiplying 1 MJ/kg by 947.817 gives 947.817 BTU/kg, which is not a unit anyone quotes. Converting the kilogram as well puts it at 429.9 BTU/lb. Stopping after the numerator leaves the answer high by a factor of 2.2, small enough to look plausible.
Therms and MMBtu are multiples
A therm is 100,000 BTU and an MMBtu is one million, where the doubled M is a Roman-numeral thousand-thousand rather than the SI mega prefix. Read MMBtu as milli-mega, or M as an SI kilo, and the result lands a thousandfold off. Check the multiple before the unit factor: about 105.5 MJ per therm, about 1055 MJ per MMBtu.