Standard Time Calculator (Time Study with Rating and Allowances)
Turn a stopwatch time study into a standard time: observed time × performance rating = normal time, plus PF&D allowance, with standard output per hour and per shift.
How it works
Normal time NT = Observed time × Performance rating · Standard time ST = NT × (1 + Allowance) (allowance as % of normal time) or ST = NT ÷ (1 − Allowance) (allowance as % of the workday) · Output per hour = 60 ÷ ST (minutes)
Standard time is the time a qualified worker needs to do a task at a normal pace, including allowances for personal needs, fatigue and unavoidable delays (PF&D). A time study measures the observed cycle time, the analyst rates how fast the worker was compared with normal pace, and the allowance is added on top. Industrial engineering texts give both allowance conventions: a percentage of normal time (multiply) or a percentage of the workday (divide), which gives a slightly longer standard for the same percentage.
Worked example
An operator is timed at an average 2.50 minutes per cycle and rated at 110%, so the normal time is 2.50 × 1.10 = 2.75 minutes. With a 15% PF&D allowance on normal time the standard time is 2.75 × 1.15 = 3.16 minutes (189.7 seconds). That is a standard output of 60 ÷ 3.1625 = 18.97 units per hour, or 151.8 units in an 8-hour shift.
Sources: Time and motion study — normal and standard time · ILO — Introduction to Work Study (Kanawaty, 4th ed.)
Frequently asked questions
How do you calculate standard time?
Multiply the average observed time by the performance rating to get normal time, then add the allowance: standard time = normal time × (1 + allowance). 2.5 min × 110% × 1.15 = 3.16 min.
What is a performance rating in a time study?
The analyst’s judgement of the worker’s pace compared with normal: 100% is normal, 120% means 20% faster than normal. Rating corrects the observed time so the standard does not depend on whether a fast or slow worker was studied.
What allowance percentage should I use?
Personal allowances are often about 5%, fatigue 4–10% depending on effort and environment, and delays a few percent more. Total PF&D allowances of 10–20% are common in light manufacturing; heavy or hot work can justify more.
What is the difference between normal time and standard time?
Normal time is the time at normal pace with no breaks. Standard time adds allowances for personal needs, fatigue and delays, so it is the figure used for planning, staffing and incentive pay.
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This calculator is for educational purposes. Double-check important results before acting on them.