How to use the line balance efficiency calculator
An assembly line runs at the speed of its slowest station, not its fastest. Enter the task time for each station and this calculator divides total task time by the number of stations times the bottleneck time, then reports the bottleneck itself, achievable output per hour, and a smoothness index.
Efficiency near 100 percent means every station carries a similar load. A low number means one or two stations hold most of the work while everyone else waits. Assembly lines are generally treated as healthy above 85 percent, and anything under 70 percent is a clear signal to redistribute tasks or split an operation.
The usual fix is moving elements out of the bottleneck and into stations with slack. Buying a faster machine for the bottleneck alone simply promotes the next longest station, so look at the whole distribution before spending money. The smoothness index summarizes that distribution in a single figure.
Time each station over several cycles and use the average rather than a single observation. When operator skill or incoming part condition varies widely, the calculated efficiency swings just as much.
Frequently asked questions
Assembly lines are usually considered healthy above 85 percent. Below 70 percent the work is piled onto one or two stations, and the fix is redistributing tasks or splitting an operation.
Only until the next longest station becomes the new bottleneck. Moving part of the bottleneck work to a station with slack usually buys more throughput than buying a faster machine.
It is the root of the summed squared gaps between each station and the bottleneck. The closer it sits to zero, the more evenly the workload is spread across stations.