Battery Cranking Amps Calculator

Work out battery cranking amps instantly with clear inputs, formula shown and shareable results.

About Battery Cranking Amps Calculator

Cranking demand scales with displacement and is much higher for diesels because of their compression ratio: roughly 230 A per litre against 160 for petrol. Cold makes it worse from both directions — the oil thickens while the battery's available current falls.

Formula

Cranking requirement

CCA required = displacement x amps per litre x cold factor

Worked example

With the default values below, Battery Cranking Amps Calculator returns Cold cranking amps required of 529. Change any input above and every figure here is recalculated in your browser.

Inputs used

Engine displacement: 2 L
Fuelone of Petrol, Diesel: Diesel
Coldest expected temperature: -15 °C
Battery CCA rating: 680 A

Results

Cold cranking amps required: 529 A
Margin over the requirement: 151 A
Capacity available at that temperature: 65.0% %
Assessment: Comfortable margin

Step by step

1Values used
2Cranking requirement
3Cold cranking amps required= 529 A
4Margin over the requirement= 151 A
5Capacity available at that temperature= 65.0 %
6Assessment= Comfortable margin

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why do diesels need more cranking current?

Compression ratios of 16-22:1 demand far more torque to turn over, and glow plugs draw current at the same time.

Can I fit a higher CCA battery?

Yes, provided it fits physically and the terminals match. A higher rating gives margin and does not harm the charging system.