Car Battery CCA Calculator

Cold Cranking Amps (CCA) is the most important battery specification for cold-weather reliability. It measures how much current a fully charged 12V battery can deliver for 30 seconds at −18°C (0°F) while maintaining a voltage of at least 7.2V (1.2V per cell).

The CCA requirement formula: Required CCA ≈ Engine Displacement (L) × Cranking Amps per Liter

General rule of thumb:

• Gasoline engines: ~100–125 CCA per liter of displacement
• Diesel engines: ~200–220 CCA per liter (diesel requires much higher compression force)

More precise formula using temperature: CCA_adjusted = CCA_rated / (1 + 0.008 × (T_rated − T_actual))

Where:

• CCA_rated = rated CCA at −18°C
• T_rated = −18°C (the test standard)
• T_actual = your actual operating temperature (°C)
• 0.008 = approximate capacity loss coefficient per degree Celsius

Battery capacity drops roughly 0.8% per °C below the rating temperature. At −30°C, a 600 CCA battery performs like a ~500 CCA battery.

Worked example: A 3.5L V6 gasoline engine in a region that reaches −25°C: Base requirement = 3.5 × 120 = 420 CCA minimum at −18°C Temperature penalty: 420 / (1 + 0.008 × (−18 − (−25))) = 420 / 1.056 ≈ 398 adjusted Add a 20% safety margin → purchase 500+ CCA battery

CCA rating systems:

• SAE (BCI) — North American standard at −18°C
• EN (European) — tested at −18°C, slightly different discharge conditions; EN ≈ SAE × 0.85
• DIN — older German standard at −18°C; DIN ≈ SAE × 0.80

Always buy at or above the vehicle manufacturer’s minimum CCA specification.