Enter partial innings as .1 or .2. So 5 and a third innings would be 5.1.
In baseball, earned run average (ERA) is the average number of runs a pitcher allows per nine innings. This stats is used as a measure of a pitcher's expected effectiveness since each game is nine innings. Runs scored as a result of an error by a fielder do not count. These are called unearned runs.
Formula: ERA = 9 * (RUNS / INNINGS)