Assuming an inverter efficiency of 90%,multiply the total Watt-Hours/Day by 1.1 to allow for inverter power loss
Your inverter may be worse or perhaps better, therefore you can adjust the efficiency factor.
Remember, an inverter used for small loads is less efficient than when being used under higher loads.
Point to remember: Connecting batteries in series (positive of one to negative of the next) adds the voltages and does not increase the Amp-Hours of the battery bank. Connecting batteries in parallel (all negatives together and all positives together) adds the Amp-Hours but does not change the battery bank voltage. A battery bank may have batteries in series strings, which are then connected in parallel to increase Amp-Hour capacity. A battery bank with the fewest number of cells (or batteries) is preferred over one with many batteries or strings in parallel connection.