CalZone Logo
User
Home Finance Toolkit

UK Gas Bill Calculator

Convert your meter readings into kWh and calculate exactly what your next gas bill should be, including 5% VAT and daily standing charges.

Enter Readings

If your meter has 4 main digits, it is likely Imperial. If it has 5, it is likely Metric.

Bill Summary

Estimated kWh Used0.00 kWh
Gas Used Cost£0.00
Standing Charge Total£9.18
VAT (5%)£0.46
Estimated Total Bill:
£9.63

Gas Bill Factors

  • Metric vs Imperial

    Older imperial meters measure in cubic feet, whilst new metric ones use cubic meters. The conversion calculation varies heavily between them.

  • Calorific Value

    This figure (usually between 37.5 - 43.0) reflects the heating power of the gas supplied to your area.

  • VAT

    Domestic energy in the UK is subject to a reduced VAT rate of 5%, not the standard 20%.

How to Calculate Your UK Gas Bill Manually

Unlike electricity, which is metered directly in kilowatt-hours (kWh) — the unit you are billed for — gas meters measure volume. To figure out how much you owe, you have to convert the volume of gas your meter recorded (in either cubic meters or cubic feet) into kWh.

The UK Standard Gas Conversion Formula

The formula used by energy companies can look daunting. Here is exactly what is happening in the background of our calculator:

  1. Find the volume: Subtract your previous reading from your current reading.
  2. Convert Imperial (If Applicable): If you have an older meter measuring in hundreds of cubic feet (ft³), you must multiply the volume by 2.83 to convert it to cubic meters (m³).
  3. Volume Correction Factor: Multiply by 1.02264 (This accounts for temperature and pressure changes).
  4. Calorific Value: Multiply by your local calorific value (usually ~39.5). This represents the energy density of the gas.
  5. Convert to kWh: Divide the final number by 3.6.

What Are Standing Charges?

Your standing charge is a fixed daily cost that you pay regardless of whether you use any gas at all. It covers the cost of maintaining the pipes, running the national grid, and meter maintenance. Therefore, your total bill is your (Total kWh * Unit Rate) + (Days in Billing Period * Daily Standing Charge).

Why is my bill an estimate?

Your supplier will use exact decimal figures for the Calorific Value specific to your region on the exact day. Our calculator uses the UK national average of 39.5 to give you an extremely accurate estimate, but the final penny amount may differ slightly from your official bill.