The quick determination of battery capacity by indirect measurements is a highly desired feature in the industry. In this poster, a dataset is presented consisting of six 2.6 Ah (1C) cells, aged under different conditions for 1000 equivalent cycles. A strong positive correlation is detected between the measured discharge capacity at 1C and the capacitance (negative imaginary part of impedance) at frequencies below 10 Hz using impedance spectroscopy (EIS). The analysis of data obtained at 2.5 Hz, which carries the best information, show that the capacitance increase has a linear relation with capacity loss for 1C cycling at 100% DOD. The implementation of this simple test would require less than a second for the determination of the capacity, instead an hour, providing good accuracy for the capacity estimation.