CALCULATORS · FIELD SERVICE KPIS
MTTR Calculator: Mean Time to Repair Formula and Worked Example
Mean time to repair is the average time one repair takes. Enter the total repair hours and the number of repairs for the same period, and the calculator returns the average.
How to use the calculator
- Decide which clock you are measuring, and use it for every repair. The formula section below explains the two common choices.
- Add up the repair time for every repair in the period and enter it under total repair hours. Decimals are fine, so 2.5 means two and a half hours.
- Count the repairs in the same period and enter the number under number of repairs. It takes a whole number.
- Read the average under the form. It updates as you type. An empty field asks for a value and never counts as zero.
The formula
- In words: MTTR = total repair time ÷ number of repairs
- In symbols: MTTR = T ÷ N, in hours
The clock is a choice. The glossary entry measures from the moment a fault is reported to the moment the equipment works again. Many teams measure only the on-site repair time. Either can be useful, and the number is only comparable when you use the same window every time. The worked example uses on-site repair time.
If the number of repairs is zero there is nothing to average, so the calculator says so instead of showing 0 hours.
The result appears in decimal hours and also as hours and minutes.
Worked example: 41 repair hours over 13 repairs
A team spent 41 hours of on-site repair time across 13 repairs in a week. MTTR is 41 ÷ 13, or 3.15 hours (3 h 9 min).
| Total repair hours | 41 |
|---|---|
| Number of repairs | 13 |
| MTTR | 3.15 hours (3 h 9 min) |
An average hides the spread. Two teams can both report the same MTTR with very different repair times, so look at the individual repairs next to the average.
What moves the number
The average moves when the repairs get faster or slower, and also when the measurement window changes.
- The clock: counting from the fault report adds travel and waiting time that on-site timing leaves out.
- Parts availability: if the window includes waiting for a part, a stocking gap shows up directly in the average.
- Diagnosis time: a repair that starts with a long search for the fault takes longer than the same repair with the cause already known.
- The mix of repairs: a week with a few large repairs and a week of quick ones produce different averages from the same team.
Frequently asked questions
How do you calculate MTTR?
Divide the total repair time by the number of repairs in the same period. With 41 repair hours over 13 repairs, MTTR is 41 ÷ 13, or 3.15 hours (3 h 9 min).
Should MTTR include travel and waiting time?
That depends on the clock you pick, and the choice changes the answer. The glossary entry measures from the fault being reported to the equipment working again, which includes travel and waiting. Many teams measure on-site repair time only. Pick one, write it down and use it for every repair.
Why does the calculator show no MTTR when the number of repairs is zero?
With no repairs there is nothing to average, so MTTR does not exist for that period. Showing 0 hours would suggest repairs happened instantly. The calculator asks for at least one repair instead.