Key Points: 8 • The change in electron kinetic entropy per particle is calculated for 22 shock cross-9 ings having wide range of shock conditions 10 • The entropy change displays a strong dependence on the electron beta parame-11 ter 12 • The entropy change corresponds to an adiabatic index γ e = 1.595 ± 0.036 13 Corresponding author: Martin Lindberg, [email protected] 14 We use Magnetospheric Multiscale (MMS) data to study electron kinetic entropy across 15 Earth’s quasi-perpendicular bow shock. We have selected 22 shock crossings covering a 16 wide range of shock conditions. Measured distribution functions are calibrated and cor-17 rected for spacecraft potential, secondary electron contamination, lack of measurements 18 at the lowest energies and electron density measurements based on the plasma frequency 19 measurements. The change in electron kinetic entropy per particle is calculated for 22 20 shock crossings. 20 out of 22 crossings display an increase in the electron kinetic entropy 21 per particle ranging between 0.1-1.4 k B while two crossings display a slight decrease of 22-0.06 k B. We observe that the change in electron kinetic entropy, ∆S e , displays a strong 23 dependence on the change in electron temperature, ∆T e , and the upstream electron plasma 24 beta, β e. Shocks with high ∆T e are found to have high ∆S e. Shocks with low upstream 25 electron plasma betas are associated to higher ∆S e than shocks with large electron plasma 26 beta. We show that the calculated entropy per particle is strictly less than the maximum 27 state of entropy obtained using a Maxwellian distribution function. The resulting change 28 in electron kinetic entropy per particle ∆S e , density ∆n e and temperature ∆T e is used 29 to determine a value for the adiabatic index of electrons. We find that an adiabatic in-30 dex of γ e = 1.595 ± 0.036 describes the observations best.