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Multiple conversions
To convert from Gigajoule (GJ) to Watt-second (Ws), use the following formula:
Watt-second (Ws)
= 109× Gigajoule (GJ)
To convert from Gigajoule (GJ) to Watt-minute (Wm), use the following formula:
Watt-minute (Wm)
= 109 × 160× Gigajoule (GJ)
= 16666666.666666666667× Gigajoule (GJ)
To convert from Gigajoule (GJ) to Watt-hour (Wh), use the following formula:
Watt-hour (Wh)
= 109 × 160 × 60× Gigajoule (GJ)
= 277777.77777777777778× Gigajoule (GJ)
To convert from Gigajoule (GJ) to Milliwatt-hour (mWh), use the following formula:
Milliwatt-hour (mWh)
= 109 × 13.6× Gigajoule (GJ)
= 277777777.77777777778× Gigajoule (GJ)
To convert energy from gigajoules (GJ) to kilowatt-hours (kWh), multiply by 277.78.
The factor is the exact ratio of the two definitions: a kilowatt-hour is 1,000 W × 3,600 s = 3.6 megajoules, so one gigajoule contains 1,000 ÷ 3.6 = 277.777… kWh. Nothing about the energy changes — only the accounting unit.
A district-heating bill shows 45 GJ of heat delivered over the winter quarter. To compare that against what a heat pump would draw from the electricity meter:
That three-step pattern — GJ to kWh, then divide by efficiency — is the core arithmetic of heating-electrification studies.
| GJ | kWh |
|---|---|
| 1 | 277.78 |
| 5 | 1,388.9 |
| 10 | 2,777.8 |
| 45 | 12,500 |
| 100 | 27,778 |
| 1,000 | 277,778 |
Energy that arrives as fuel or heat is accounted in joules; energy that arrives through a wire is accounted in kWh — and comparisons between the two always route through this factor. District-heating utilities in Scandinavia, the Baltics and Canada bill customers in GJ; national energy balances, IPCC inventories and fuel heating values are tabulated in GJ or TJ; and one common natural-gas trading unit is the gigajoule (Canadian gas prices are quoted in dollars per GJ). Meanwhile every appliance, solar array and battery is rated in kWh. Whether the question is "how many rooftop-solar kilowatt-hours replace one GJ of gas heating?" (278, before efficiency corrections) or "what is 1 GJ worth at retail electricity prices?", the ×277.78 step comes first. A round-number anchor makes estimates fast: 1 GJ ≈ 280 kWh, and 3.6 GJ is exactly 1,000 kWh (1 MWh).
To convert energy from gigajoules (GJ) to megawatt-hours (MWh), divide by 3.6.
The factor is exact: one watt-hour is 3,600 joules, so a megawatt-hour is 3,600 MJ = 3.6 GJ. The clean anchor runs in both directions — 3.6 GJ = 1 MWh, and 1 GJ = 0.2778 MWh.
An industrial site's gas contract delivers 12,000 GJ per year, and an electrification study wants the figure beside the site's electricity use in MWh:
If the site also buys 2,800 MWh of electricity, gas still carries the majority of its energy — the kind of like-for-like statement this conversion exists to enable.
| GJ | MWh |
|---|---|
| 1 | 0.278 |
| 3.6 | 1 |
| 100 | 27.8 |
| 1,000 | 277.8 |
| 12,000 | 3,333 |
| 100,000 | 27,778 |
Gas is sold in gigajoules; electricity is sold in megawatt-hours; every decarbonization, cogeneration or fuel-switching study must therefore route through ÷3.6 before its numbers can share a chart. Canadian and Australian gas invoices state GJ directly, European ones state kWh or MWh already, and international statistics (IEA balances, IPCC inventories) tabulate joules — so the conversion appears wherever these worlds meet: comparing heat pumps against boilers, converting a CHP plant's fuel input to the same units as its electrical output to compute efficiency, or translating a data center's gas-fired backup consumption for a sustainability disclosure. Two cautions keep the comparisons honest. First, the conversion equates energy content, not usefulness — 3.6 GJ of gas through a 90% boiler delivers less heat than 1 MWh of electricity through a COP-3.5 heat pump, and the interesting analysis starts after the unit conversion, not at it. Second, gas volumes must already be in energy terms; a cubic meter of natural gas holds roughly 0.038 GJ, and skipping that step leaves the ÷3.6 operating on the wrong quantity entirely.
To convert from Gigajoule (GJ) to Gigawatt-hour (GWh), use the following formula:
Gigawatt-hour (GWh)
= 109 × 160 × 60 × 109× Gigajoule (GJ)
= 0.00027777777777777777778× Gigajoule (GJ)
To convert from Gigajoule (GJ) to Joule (J), use the following formula:
Joule (J)
= 109× Gigajoule (GJ)
To convert from Gigajoule (GJ) to Kilojoule (kJ), use the following formula:
Kilojoule (kJ)
= 109 × 11000× Gigajoule (GJ)
= 106× Gigajoule (GJ)
To convert from Gigajoule (GJ) to Megajoule (MJ), use the following formula:
Megajoule (MJ)
= 109 × 1106× Gigajoule (GJ)
= 1000× Gigajoule (GJ)
To convert from Gigajoule (GJ) to calorie (cal), use the following formula:
calorie (cal)
= 109 × 14.184× Gigajoule (GJ)
= 239005736.13766730402× Gigajoule (GJ)
With 14.184 is the ratio between the base units calorie (cal) and Joule (J).
To convert from Gigajoule (GJ) to Kilocalorie (kcal), use the following formula:
Kilocalorie (kcal)
= 109 × 14.184 × 11000× Gigajoule (GJ)
= 106 × 14.184× Gigajoule (GJ)
= 239005.73613766730402× Gigajoule (GJ)
With 14.184 is the ratio between the base units calorie (cal) and Joule (J).
Ever looked at your energy bill and wondered what a Gigajoule (GJ) is?
It's a standard unit used to measure energy, just like a kilowatt-hour is for electricity or a gallon is for gasoline.
Specifically, a Gigajoule (GJ) is a metric unit of energy in the International System of Units (SI).
One gigajoule is equal to one billion Joules (109 J).
A single gigajoule contains a significant amount of energy. To put it into perspective, one GJ is roughly equivalent to:
This makes it an efficient unit for measuring large-scale energy consumption, such as heating your home or powering industrial processes.
You'll most commonly encounter the gigajoule in a few key areas:
Understanding how the gigajoule compares to other units helps compare the costs and efficiencies of different energy sources.
Here are some key gigajoule conversions: