how long will a 9v battery last??????

is there a way to find out how long a 9v battery will last given x amount of current? lets just say 10mA

thanks.

That depends upon the battery model (type) and its associated capacity. For example, Eveready's Energizer e2 (model X22) is rated at 655mAh, while the standard Energizer alkaline (model 522) is rated at 625mAh. Their carbon-zinc equivalent (model 1222) is rated at 400mAh, and their NiMH rechargeable equivalent (model NH22) is rated at only 150mAh.

You can look at all of Eveready's specs here...

BTW -- according to the datasheet for the X22, approximate service life at 10mA constant current drain is listed below for the plotted cutoff voltages:

10mA draw to 7.0V cutoff --> approximately 45 hours
10mA draw to 6.0V cutoff --> approximately 58 hours
10mA draw to 4.8V cutoff --> approximately 65 hours

Eveready rates their battery products in this category to a cutoff voltage of 0.8V/cell, meaning 4.8V for the 9V models.