Approximative calculation for power supply to Arduino Car


I need some advises for a technical design of an arduino car (2Wheels).
How can I do an approximative calculation for the power supply (2 Electro motors and 1 Arduino Board, 1 Motor Shield, 1 Bluetooth-Module).

Everybody just uses 4x 1,5V Batteries but nobody gives a reason why they are using this one.

I would calculate the power the electro motors need in a sceond but I can not find any details for my calculation.

You can find my chassis with electro motors by following the link:

Thank you.

Those motors are intended for battery operation, and 5 to 6V (4X AA) is fine for most purposes.

The battery lifetime depends on the size of the batteries and average current draw, which you can measure with a multimeter.

Approximate battery lifetime in hours = (battery capacity in mAh)/(average current draw in mA)