Turn your gas meter reading in cubic metres or cubic feet into kilowatt hours, then see what it costs. Uses the official gov.uk conversion factors.
Subtract your old meter reading from the new one to get the units used, then enter it here.
If you just want the shortcut, here it is. One cubic metre of gas is about 11.2 kWh. One cubic foot is about 0.32 kWh, so 100 cubic feet is roughly 31.8 kWh. Those figures assume a typical calorific value, so they'll be within a percent or two of what your supplier bills. For the exact number, use the calculator above with the calorific value printed on your bill.
Your gas meter measures volume, but you're billed for energy in kilowatt hours. The conversion is set out in law, in the Gas (Calculation of Thermal Energy) Regulations 1996, and explained in plain terms on the gov.uk gas bill calculation guidance. Here are the steps.
Put together, the metric formula is: cubic metres multiplied by calorific value, multiplied by 1.02264, divided by 3.6. For an imperial meter you add the 0.0283 step at the start.
Say your metric meter read 4,850 last month and reads 4,950 now. That's 100 cubic metres used. At a calorific value of 39.5, the sum is 100 times 39.5 times 1.02264, divided by 3.6, which comes to about 1,122 kWh. At the October 2026 gas rate of 7.97p per kWh, that's £89.43 for the gas alone, before the daily standing charge.
A metric meter shows "m3" next to the numbers and separates the black digits from the red part-units with a decimal point. An imperial meter shows "cubic feet" or "ft3" and often has old-style revolving dials. All meters fitted since 1995 are metric, and the smart meter rollout has replaced most of the remaining imperial ones. If you read an imperial meter in hundreds of cubic feet, multiply by 2.83 to get cubic metres instead of by 0.0283.
Not all gas is identical. The energy content depends on the mix of methane and other hydrocarbons in the supply. National Grid measures the calorific value across the network and passes it to suppliers for billing. Because gas transporters have to keep it between 38 and 41 MJ/m3, the difference between the lowest and highest values changes your kWh figure by only about 7%. The exact number used for your bill is printed on it, usually near the meter readings. Enter that figure in the calculator for the most accurate result.
Once you know your kWh, you can check your bill is right, compare tariffs (all UK energy prices are quoted per kWh), or work out running costs. If you want to see how your gas rate compares to the Ofgem price cap, or check whether you're overpaying, try our cost per kWh checker. For electricity, our appliance running cost calculator does the same job for individual devices.
Multiply the cubic metres used by the calorific value (about 39.5), then by 1.02264, then divide by 3.6. For an imperial meter, convert cubic feet to cubic metres first by multiplying by 0.0283. As a rule of thumb, one cubic metre is about 11.2 kWh.
The meter measures volume, but you pay for energy. Suppliers convert the volume you use into kilowatt hours using the calorific value and a correction factor, as required by the 1996 regulations.
Gas expands and contracts with temperature and pressure, so the measured volume is adjusted to standard conditions using this factor. It's set in law and shown on your bill.
A metric meter shows m3 and a decimal point. An imperial meter shows cubic feet and often has dials. New meters are all metric.
Conversion factors from the gov.uk gas bill calculation guidance and the Gas (Calculation of Thermal Energy) Regulations 1996. Gas price based on the Ofgem October 2026 price cap. For meter reading help see Citizens Advice.