Electricity Bill Calculator
Calculate your monthly electricity bill from units consumed using tiered slab rates, a fixed charge and tax. See the full slab-by-slab breakdown instantly.
Updated 2026-06-14 · Free · No sign-up · Runs privately in your browser
Enter your units consumed (kWh) and your tariff slabs. Leave a slab limit blank for "no upper limit". All money figures use your own currency.
Show the formula & steps
How the Electricity Bill Calculator Works
This calculator estimates your monthly electricity bill the way most utilities actually bill you: with tiered slab rates, a fixed charge and a tax or duty on top. Enter the units consumed (kWh), fill in your tariff’s slab limits and per-unit rates, and it returns the energy charge, the tax, and the total bill with a slab-by-slab breakdown.
Because you supply your own rates, it works for any provider and any currency — just copy the numbers from your tariff sheet.
The Formula
Energy charge = Σ (units in slab × slab rate) Subtotal = energy charge + fixed charge Total bill = subtotal × (1 + tax%)
Only the units that fall inside each band are charged at that band’s rate. The first slab covers the first block of units, the second slab the next block, and so on; any units above the final slab limit are charged at the top rate.
Worked Example
Suppose you used 450 kWh with these slabs: first 100 units at 3, next 100 at 4.5, next 200 at 6, and any extra at 7.5, plus a 100 fixed charge and 5% tax:
- Slab 1: 100 × 3 = 300
- Slab 2: 100 × 4.5 = 450
- Slab 3: 200 × 6 = 1,200
- Slab 4: 50 × 7.5 = 375
- Energy charge = 300 + 450 + 1,200 + 375 = 2,325
- Subtotal = 2,325 + 100 fixed = 2,425
- Tax = 2,425 × 5% = 121.25
- Total bill = 2,546.25
Slab Breakdown
| Slab | Units charged | Rate | Cost |
|---|---|---|---|
| 1 (first 100) | 100 | 3.00 | 300.00 |
| 2 (next 100) | 100 | 4.50 | 450.00 |
| 3 (next 200) | 200 | 6.00 | 1,200.00 |
| 4 (remaining) | 50 | 7.50 | 375.00 |
The breakdown makes it clear that the last units are the most expensive, so trimming usage when you are deep in a high slab saves the most money. For appliance-level running costs try the electricity cost calculator, and explore more money tools in our finance calculators hub.
Frequently asked questions
How is an electricity bill calculated from units?+
Most utilities use tiered (slab) pricing. Your total units (kWh) are split across bands, and each band is charged at its own rate. Add the cost of every band to get the energy charge, add any fixed or service charge, then apply tax or duty as a percentage to reach the final bill.
What is slab or tiered electricity pricing?+
In slab pricing the first block of units costs the least and each higher block costs more per kWh, to encourage conservation. For example the first 100 units might cost 3 per unit, the next 100 cost 4.5, and so on. Only the units that fall inside each band are charged at that band's rate.
What is the fixed charge on my bill?+
The fixed (or service/demand) charge is a flat monthly fee you pay regardless of how much electricity you use. It covers metering, billing and grid maintenance. Enter it separately so it is added once, before tax, on top of the per-unit energy charge.
Does this calculator work for any country?+
Yes. Because you enter your own slab limits, per-unit rates, fixed charge and tax percentage, it works for any utility in any currency. Copy the slabs straight from your tariff sheet or a recent bill and the result will match your provider's method.
How can I lower my electricity bill?+
Reducing units consumed is the most effective lever, especially when you are in a higher-priced slab, because those last units cost the most per kWh. Shift heavy loads off-peak if you have time-of-use rates, switch to efficient appliances and LED lighting, and check the fixed charge when comparing tariffs.