Operations Management and Strategic Management · Control Measures - Time and Motion Study, Method Study, Work Study

Standard Time Calculation: Rating and Allowances

Updated 10 October 2026 · Fact-checked

Standard time is the time a qualified worker, working at a normal pace, needs to complete a job, including allowances. You find it in steps: observed time gives basic time, rating converts it to normal time, and adding allowances gives standard time. Normal time = basic time × rating ÷ 100.

Understand Standard Time Calculation: Rating and Allowances

Work measurement tries to answer one question: how long should a job take? A stopwatch gives you the observed time, but a fast worker and a slow worker will record different times for the same job. You need a fair, common yardstick.

That yardstick is normal time. It is the time a worker of average skill would take, working at a normal pace, without any extra rest. To reach it, the analyst judges the worker's speed against a benchmark pace. This judgement is called performance rating. A rating of 100 means normal pace. Above 100 means faster than normal. Below 100 means slower.

No one can work without a break. Workers need rest, personal time, and sometimes time lost to unavoidable delays. So you add allowances to normal time. The result is standard time: the time allowed for the job in planning, costing and incentive schemes.

So the chain is: observed (basic) time → rated to normal time → allowances added → standard time. Each step has one job. Keep them separate and the numerical becomes easy.

In many questions the term basic time is used for the observed time per element (often after averaging). Some books call the rated time 'basic time' as well. Always read the question's wording and check which meaning it gives.

Key rules to remember

Normal time (basic time rated): Normal time = Observed time × (Rating ÷ 100); Rating is on a scale where 100 is normal pace. Apply it to each element's time.
Standard time with allowance as % of normal time: Standard time = Normal time × (1 + Allowance %); Use when the question says allowance is a percentage of normal time.
Standard time with allowance as % of standard time: Standard time = Normal time ÷ (1 − Allowance %); Use when allowance is stated as a percentage of the total (standard) time, or of the working day.
Average observed time: Average observed time = Σ observations ÷ number of observations; Do this first if several readings are given for an element. Exclude abnormal readings if the question tells you to.
Standard time of a job: Job standard time = Σ standard time of all elements; Add elements after rating and allowances. Add any contingency or fatigue allowance as the question states.

How to solve Standard Time Calculation: Rating and Allowances questions

Use this order for any standard time question. It keeps the working clean and earns step marks.

1Read what time is given: observed, basic, or already rated. Note the unit (minutes or hours).
2If there are several readings for an element, drop any readings the question calls abnormal and find the average observed time.
3Multiply by rating ÷ 100 to get normal time for each element. Total the elements if needed.
4Find the total allowance percentage (relaxation + contingency + others). Add them if given separately.
5Check the base of the allowance. If it is on normal time, multiply by (1 + %). If on standard time or on the working day, divide by (1 − %).
6Compute standard time per unit, and add any element that is not rated (for example machine time).
7Answer the final ask: units per day, output per hour, or labour cost. Write units clearly.

Quickest way: Rate, add allowance, convert

When to use it: Use for single-job questions with one rating and one allowance, especially MCQs.

Normal time = observed × rating ÷ 100.
Look at the phrase after 'allowance': 'of normal time' means multiply by 1.xx; 'of total time' or 'of the day' means divide by 0.xx.
Standard time = result. For output, divide available minutes by standard time per unit.
Sanity check: standard time must be greater than normal time, and a rating above 100 must raise the time.

Common mistakes in Standard Time Calculation: Rating and Allowances

Adding the allowance to observed time instead of normal time.
Students skip the rating step because it feels like extra work.
Fix: Always write normal time as its own line before touching allowances.
Using the wrong base for the allowance percentage.
Students always multiply by (1 + %) out of habit.
Fix: Check whether the allowance is on normal time or on standard time. If on standard time, divide by (1 − %).
Dividing by the rating instead of multiplying.
Confusing rating with a efficiency-style ratio.
Fix: A worker rated 120 is faster, so the observed time understates normal time. Multiply: normal time is longer than observed.
Applying rating to machine-controlled time.
Rating is applied blindly to every element.
Fix: Rating measures human effort. Do not rate elements the machine controls unless the question says so.
Forgetting to average several readings, or including abnormal ones.
Students rush to the formula.
Fix: Average first. Leave out readings the question marks as abnormal, and state this in your working.
Mixing up units when finding output per day.
Standard time is in minutes but the shift is in hours.
Fix: Convert the shift to minutes before dividing.

Worked examples

Example 1

A time study of a job gives an observed time of 4.5 minutes per piece. The worker's performance rating is 120. Relaxation and other allowances are 15% of normal time. Find the standard time per piece.

Show the solution

Normal time = 4.5 × 120 ÷ 100 = 5.4 minutes.
Allowance = 15% of 5.4 = 0.81 minutes.
Standard time = 5.4 + 0.81 = 6.21 minutes.

Answer: Standard time = 6.21 minutes per piece.

Example 2

For an element, five readings (minutes) were recorded: 2.0, 2.2, 3.5, 2.1, 1.9. The reading 3.5 was due to a tool breakage and is abnormal. The worker's rating is 90. Allowances are 10% of standard time. How many pieces can be produced in an 8-hour shift if the whole job is this single element?

Show the solution

Exclude 3.5. Remaining readings: 2.0, 2.2, 2.1, 1.9. Sum = 8.2.
Average observed time = 8.2 ÷ 4 = 2.05 minutes.
Normal time = 2.05 × 90 ÷ 100 = 1.845 minutes.
Allowance is on standard time, so standard time = 1.845 ÷ (1 − 0.10) = 1.845 ÷ 0.9 = 2.05 minutes.
Note: standard time equals the average observed time here only by coincidence. Rating 90 gives × 0.9, and a 10% allowance on standard time gives ÷ 0.9, so the two cancel (0.9 × 1/0.9 = 1). With other ratings or allowances they will differ.
Shift = 8 × 60 = 480 minutes.
Pieces = 480 ÷ 2.05 = 234.15, so about 234 complete pieces.

Answer: Standard time = 2.05 minutes per piece; output = 234 pieces per 8-hour shift.

Exam tips

Write the chain as headings: observed time, normal time, allowance, standard time. Step marks follow each line.
Underline the base of the allowance in the question before calculating.
In MCQs, check the direction: rating above 100 raises normal time, below 100 lowers it. Use this to reject wrong options fast.
Round only at the end, and state the unit (minutes per unit, units per shift).
For theory, be ready to define performance rating, normal time and standard time, and name common allowances such as relaxation, contingency and fatigue.

Practice questions from Control Measures - Time and Motion Study, Method Study, Work Study

Standard Time Calculation: Rating and Allowances: frequently asked questions

What is the difference between basic time, normal time and standard time?

Basic (observed) time is what the stopwatch records for the element. Normal time is basic time adjusted by the performance rating to a normal pace. Standard time is normal time plus allowances. Some books use 'basic time' for the rated time, so check the question's wording.

What is performance rating in time study?

It is the analyst's judgement of a worker's pace compared with a normal pace. A rating of 120 means the worker is 20% faster than normal, so the observed time is scaled up to reach normal time. A rating of 100 means normal.

What allowances are added to normal time?

Common ones are relaxation allowance for rest and personal needs, contingency allowance for small unavoidable delays, and sometimes allowances for fatigue, special conditions or policy. Add them together as a percentage unless the question treats them separately.

Should I divide or multiply when adding an allowance percentage?

Multiply by (1 + %) if the allowance is a percentage of normal time. Divide by (1 − %) if it is a percentage of standard time or of the total working time. The wording of the question decides.