# Calculate Your Gas Bill Online

Your gas meter provides data in cubic feet or meters. Readings are taken then converted to kilowatt hours (kWh) for billing purposes. If you have your meter readings to hand, then enter your data into the calculator below to estimate your next bill.

**Note:** Imperial meters measure in hundreds of cubic feet (100 ft³). If your meter shows a usage of 1, you've actually used 100 ft³.

If you enter "1" into the imperial meter calculator and "2.83" into the metric calculator, you get the same kWh usage because 100ft³ equals 2.83m³.

## Calculations Explained

**The Multiplier factor** converts imperial to metric. 2.83 feet equals one meter.
**The Conversion factor** is an industry figure to account for atmospheric pressure.
**The Calorific value** adjusts for changes in the composition of gas when burned.
**The kWh conversion** 1-kilowatt hour is equivalent to 3.6 million joules.

Note: The gas measurement is joules, so the above calculation automatically converts to kWh by dividing by 3.6.

## Worked Examples

A previous meter reading of 7,380 with a current reading of 7,842 equals a difference of 482 units. Here's how you convert gas units to kWh.

### Imperial Calculation

Here's how to convert cubic feet (ft3) to kWh from your gas meter reading.

482 unit used X 2.83 to convert to cubic meters X 1.02264 X 39.2 calorific value divided by 3.6 provides 15,189 kWh. At 2.84p/kWh provides an estimated bill of £431.38.

482 x 2.83 x 1.02264 x 39.2 ÷ 3.6 = 15,189 x 2.84 = £431.38.

### Metric Calculation

Alternatively, convert cubic meters (m3) to kWh gas units.

482 unit used X 1.02264 X 39.2 calorific value divided by 3.6 provides 5367.27 kWh. At 2.84p/kWh provides an estimated bill of £152.43.

482 x 1.02264 x 39.2 ÷ 3.6 = 5367.27 x 2.84 = £152.43.

## Calorific Values by Supplier

These values vary a little by each supplier, are governed by legislation and provided by the National Grid. The values provided are always rounded down to the next decimal place.

The current values are British Gas 39.3, EDF 39.1, EON 39.2, ScottishPower 39.0 and SSE 39.6.