Momentary Switch

My project is dealing with and Arduino Due that has 21 momentary switches attached to 21 digital pins no other sensors or LEDs. I am trying to calculate the type of battery we would need for the system. Am I correct in the fact that since they are just switches there is very little current draw from the switches and I should really only look at the current draw from the DUE? I put a multimeter on the switches and read the current and it was very small but I might have done it wrong. This is probably a stupid question but I'm just not feeling confident in my thought process for it right now.

Thank you,

Scooter

Yes the switch current is very low.
We have to see a schematic to really tell for sure.
Here you see typical switch setups: