Car Battery State of Charge Calculator

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Enter the open circuit voltage and the temperature, in either °F or °C. The state of charge will then be calculated automatically.

Measured Voltage  VThe voltage measured accross the battery terminals when the battery is not supplying (a significant) current or being charged.
Temperature °FIdeally this would be the temperature of the battery electrolyte but if the battery has not been charged or used for a few hours the surrounding air temperature will probably be close enough.


Battery TypeState of Charge
Low Maintenance or standard (batteries with filler caps)17  %
Maintenance free, sealed, AGM or Gel cells (batteries without filler caps)26  %

This calculator uses a polynomial fit to data from "TEMPERATURE COMPENSATED BATTERY STATE-OF-CHARGE (SoC) TABLES (Revised February 5, 2014)" downloaded from

HTML 5  ✔

Whilst I try to keep the information on this site accurate, I'm only human and I do occasionally make mistakes. I therefore advise you to check any information before using it for anything important. If you do find any errors, please let me know so that I can correct them.

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This page was last changed on: 16 September 2017.

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