Bill from meter reading calculator
Estimate the usage cost between two readings, then add standing charge. Use this when a supplier reading or rebill looks wrong.
Use with
Meter reading bill estimate
39.2 is illustrative. Gas conversion uses the bill’s calorific value and volume correction factor 1.02264; imperial register units are hundreds of cubic feet. GOV.UK calculation method. Enter tax-inclusive rates; do not add VAT twice.
Use the output carefully
This is a first-pass check. Your supplier bill may include VAT, multiple rates, gas conversion, debt recovery or account adjustments. Use it to ask better questions, not as a final legal calculation.
If it does not match
The formula, and the four things people get wrong
cost = ( units × unit rate ÷ 100 ) + ( days × standing charge ÷ 100 )
| Mistake | What happens | Fix |
|---|---|---|
| Forgetting the standing charge | Your figure is £26 a month under on dual fuel. | Always add days × p/day. |
| Using the headline cap figure as a rate | £1,862 is an annual total for typical usage, not a rate. Nothing works if you multiply by it. | Use p/kWh from your bill. |
| Counting days wrong | Off by a few pounds, and it hides genuine double-billed days. | Use the supplier’s billed days and check that consecutive periods do not overlap. |
| VAT confusion | Out by exactly 5%. | Ofgem's published cap rates include VAT. Some bills quote rates excluding it and add 5% at the end. Check which yours does. |
Gas has one extra step
Gas meters measure volume, not energy. If your meter reads in cubic metres, the bill converts it:
kWh = m³ × 1.02264 × calorific value ÷ 3.6
The calorific value is printed on your bill and is typically around 39–40. The volume correction factor 1.02264 is standard. An imperial meter reading in hundreds of cubic feet is multiplied by 2.83 first to get cubic metres. In practice: use the kWh figure the bill has already calculated, and only do this arithmetic if you are checking whether the conversion itself is right.
A full worked example
Electricity, one quarter, single-rate tariff, GB average capped rates.
| Step | Working | Result |
|---|---|---|
| Opening reading, 1 July | from the bill | 38,412 |
| Closing reading, 1 October | from your meter | 39,048 |
| Units used | 39,048 − 38,412 | 636 kWh |
| Unit cost | 636 × 26.11 ÷ 100 | £166.06 |
| Days billed | 1 July to 1 October (end excluded) | 92 |
| Standing charge | 92 × 57.19 ÷ 100 | £52.61 |
| Total | £218.67 | |
| Bill says | £219.04 | |
| Difference | £0.37 — request the detailed calculation; do not assume rounding explains it. |
How big a difference should worry you? Under a pound is rounding. A few pounds usually means a rate change part-way through the period, or VAT handled differently — ask for the calculation. Tens of pounds means the readings, the days or the rates are wrong, and that is worth a proper query. Hundreds means check the readings against your meter first, before anything else.
If you have a two-rate meter
Economy 7 and similar meters have two registers, billed at different rates. Calculate each separately and add them; do not add the readings together first.
| Register | Units | Rate | Cost |
|---|---|---|---|
| Day / Normal (R1) | 412 kWh | 30.50p | £125.66 |
| Night / Low (R2) | 388 kWh | 14.20p | £55.10 |
| Standing charge | 92 days | 57.19p | £52.61 |
| Total | 800 kWh | £233.37 |
Illustrative two-rate figures — Economy 7 rates vary by supplier and region and are not the single cap rates shown elsewhere on this site. Use the rates printed on your own bill.
If your night usage looks implausibly small or your day usage implausibly large, the registers may be mapped the wrong way round. See register and clock-change errors.
Frequently asked questions
Can I use this for gas?
Yes. Select cubic metres or hundreds of cubic feet and enter the calorific value from your bill. Use electricity mode for readings already expressed in kWh.
What is it best for?
It is best for checking whether usage and cost look broadly consistent with the readings and rates shown on the bill.
How do I work out a bill from two meter readings?
Closing reading minus opening reading gives the units. Multiply by the unit rate in pence and divide by 100. Then add the days in the period times the daily standing charge, divided by 100.
My answer is a few pounds out. Is the bill wrong?
Probably not. Small differences can arise from rate precision, billed days or tax treatment; they should still be explainable. Ask for the calculation showing how the days split between rate periods.
What about a two-rate Economy 7 meter?
Calculate each register separately at its own rate and add them, plus one standing charge. Do not add the two readings together first — they are priced differently.