Battery life calculation

[dofl1234]

I am working on a project using a battery. Two questions for battery life.

Q1. How can I measure total current draw and how can I calculate battery life from that? For example, I am using feather M0 + Buzz speaker + Ultrasonic distance sensor. How to measure total current using a multimeter?

Q2. how can I calculate battery life from current data like '2.2mA' in a product page?

[adafruit_support_bill]

This guide explains how to measure current in your circuit: https://learn.adafruit.com/multimeters/current

Battery capacity is measured in milliamp-hours (mAh). 1 mAh is equivalent to 1 mA for 1 hour. To calculate battery requirements, multiply the current draw in mA by the expected run-time.

Note that the rated battery capacity assumes that you are not exceeding the 'standard' discharge rate or operating temperature range specified in the datasheet for the cell. Also note that battery capacity will degrade over the lifetime of a cell. So if your runtime requirements are critical, be sure to add in a 'safety factor'.