Calculatium

Battery Runtime Calculator

Estimate battery runtime from volts and amp-hours or watt-hours. Adjust usable capacity and efficiency, then compare two constant power loads.

Enter your values

The starting values are editable examples. Results update when you change your inputs.

Example: 12
Example: 100
Allowed range: 0 – 100
Allowed range: 0 – 100
Example: 100
Example: 200

Your result

Updates as you change your values.

Enter values to calculate.

How it is calculated

Nominal Wh = voltage × Ah, or the Wh value entered directly. Runtime in hours = nominal Wh × usable fraction × efficiency / load in watts.

Worked example

A 12 V, 100 Ah battery contains 1,200 nominal Wh. At 80% usable capacity and 90% efficiency, 864 Wh are available: 8.64 hours at 100 W or 4.32 hours at 200 W.

Before you calculate

Use compatible nominal voltage and capacity ratings. The usable percentage represents the share you intend to discharge; efficiency models conversion losses. Enter device consumption in watts and treat the second scenario as a comparison using the same available energy.

Interpreting the result

This is a constant-load energy estimate. Temperature, ageing, discharge rate, cutoff voltage, standby losses and changing demand can reduce real runtime. It does not certify battery safety, wiring or compatibility with a particular appliance.

Use the units shown beside each field. Monetary fields labelled EUR stay in euros; changing language does not exchange currencies. Results are estimates under the stated assumptions.