Battery life calculator — how long will your battery last?

Life (hours) = published capacity (mAh) ÷ average current (mA)

Data version XREFVER. Capacity is the declared value on each model page and in that model’s EU 2023/1542 information document; follow the source link to check it. Where we have not published a capacity we say so and ask you to request the data sheet — we do not estimate.

Same holder, different chemistry — how long each one lasts

Cells listed here fit the same holder. They are not interchangeable: an alkaline and a silver-oxide cell of the same size run at different voltages and hold their voltage differently. Life is calculated with your current and hours per day.

Published capacity is declared under a documented discharge condition (for our AA and AAA alkaline cells that is a 43 Ω load, 4 h per day, down to 0.9 V at 20 ± 2 °C). A higher current, a cold device or a pulsed load gives a shorter life than the figure here — treat it as the ceiling, not the promise.

How to work out battery life by hand

Divide the capacity in mAh by the average current in mA to get hours, then divide by the hours the device runs per day to get days. A CR2032 declared at 190–255 mAh driving a 0.2 mA clock therefore gives 950–1,275 hours, or roughly 40–53 days if the clock draws current around the clock.

Life in hours is capacity in mAh divided by the average current in mA; life in days is that result divided by the hours the device runs per day. A 190–255 mAh CR2032 pulling 0.02 mA therefore lasts 9,500–12,750 hours, or about 396–531 days running around the clock.

life_hours = capacity_mAh ÷ current_mA

• Capacity is the declared value for the cell — 2150–2600 mAh for our AA alkaline LR6, 1020–1260 mAh for AAA, 190–255 mAh for CR2032. Each one is on its model page and in the EU 2023/1542 information document for that model.
• Current is what the device pulls, not a property of the cell. Measure it in series with a multimeter, take it from the datasheet, or calculate it from the load: voltage ÷ resistance.
• Hours per day turns the result into calendar time. A clock that runs 24 hours a day and a torch used for one hour a day consume the same capacity at completely different rates.
• The result is a ceiling. Capacity is declared under a documented discharge condition — for our AA and AAA alkaline cells, a 43 Ω load, 4 h per day, down to 0.9V at 20 ± 2 °C. Higher current, cold and pulsed loads all shorten real life.

Because the same can size carries different chemistries with different capacities and different discharge curves. In our own data the 11.6 × 5.4 mm can holds the alkaline LR44 at 118 mAh and the silver-oxide SR44 at 175 mAh, and the 9V block holds 620–640 mAh alkaline against 320 mAh carbon-zinc. The cell you take out is the authority.

The tool above separates the two groups whenever you pick a cell, and our battery cross reference keeps the equivalent numbers apart by family: an alkaline and a silver-oxide cell of the same size fit the same holder and are not electrically equal. More detail on the chemistry trade-off is in alkaline vs zinc-carbon vs lithium and how long do batteries last.

Calculating is free and stays free. If the number you need is a price, take the cell you looked up to the contact page and the quote form arrives with the model already attached. If you are designing the product, send the drain and the service interval and we will match the cell to it.

Ask the factory Cross reference tool