Cost and Management Accounting · Service Costing

Cost Units and Cost Classification in Service Sector

Updated 4 October 2026 · Fact-checked

A cost unit in service costing is the measure used to collect and compare the cost of a service, such as bed-day, room-day, passenger-km or tonne-km. Composite units combine two measures and are found by multiplying them. Classify costs as fixed, semi-fixed or variable, then divide total cost by the units.

Understand Cost Units and Cost Classification in Service Sector

Manufacturing gives you a physical product to count. A service does not. You cannot count a hospital stay in pieces. So service costing needs a measure of service delivered. That measure is the cost unit.

A simple cost unit uses one measure. Examples: cost per consultation, cost per meal served, cost per call, cost per student. A composite cost unit uses two measures together, because one measure alone does not describe the service. A bus carries passengers over distance, so you use passenger-km. A truck carries goods over distance, so you use tonne-km. Hospitals use bed-day, and hotels use room-day.

Two more points on composite units. Passenger-km is passengers carried × distance. Tonne-km can be absolute or commercial. Absolute tonne-km adds up the actual load × actual distance for each leg of the trip. Commercial tonne-km uses the average load × the total distance of the trip. For a trip with a return journey, commercial tonne-km takes the full distance travelled (out and back) with the average load, while absolute tonne-km takes the sum of each leg. Read the question for which one it wants.

The average load must include every leg, including an empty leg with zero load. Do not work out the average on the loaded leg only. Example: a 10-tonne outward load and an empty return give an average load of (10 + 0) ÷ 2 = 5 tonnes. Commercial tonne-km is then 5 × total distance (out and back).

Costs in services are also classified by behaviour. Fixed costs do not change with activity in the relevant range, such as insurance, licence fees, garage rent and salaries of managers. Variable costs change with activity, such as fuel, tyres, and food and consumables per patient. Semi-fixed (semi-variable) costs have both parts, such as a telephone bill with a rental plus a call charge, or supervision that steps up when activity crosses a level.

Why this matters: the cost per unit depends on the unit you choose. Fixed costs are charged by time period, and variable costs by usage. Splitting them correctly lets you work out the cost per unit, fix a rate, and see how cost changes if activity changes.

Key rules to remember

Cost per unit (service): Cost per unit = Total cost for the period ÷ Total service units for the period; Use the same period for cost and units. Total cost means fixed + variable + semi-fixed parts.
Passenger-km: Passenger-km = Number of passengers × Distance travelled in km; Where passengers vary by trip, sum each trip. Ensure you count only the days or trips actually run.
Absolute tonne-km: Absolute tonne-km = Σ (load carried on each leg in tonnes × distance of that leg in km); Use the actual load on each leg. An empty return leg adds zero.
Commercial tonne-km: Commercial tonne-km = Average load in tonnes × Total distance travelled in km; Average load includes legs with zero load. Average load = (sum of loads on all legs ÷ number of legs) when legs are of equal distance. Where legs differ, use the average the question gives or says to compute. Example: 10 tonnes out and empty back gives average load 5 tonnes.
Bed-day: Bed-days = Number of beds × Days available (or occupied, as the question asks); Check whether the question wants available bed-days or occupied bed-days.
Room-day: Room-days = Number of rooms × Days available (or occupied); Occupancy % = Occupied room-days ÷ Available room-days × 100
Semi-fixed cost split: Fixed part + (variable rate × activity) = Total semi-fixed cost; If a question gives two activity levels, variable rate = Change in cost ÷ Change in activity.

How to solve Cost Units and Cost Classification in Service Sector questions

Use this order for any question on cost units or cost classification in services.

1Identify the service and pick the cost unit the question asks for. If it names none, choose the standard one (passenger-km, tonne-km, bed-day, room-day).
2Decide if the unit is simple or composite. If composite, write the two measures you will multiply.
3Compute the service units. For transport, work out each leg separately first. For hospitals and hotels, check whether you need available or occupied days.
4Classify each cost as fixed, variable or semi-fixed. Split semi-fixed costs into their fixed and variable parts using the data given.
5Convert annual or monthly costs to the same period as the units. For example, divide an annual cost by 12 for a month.
6Total the costs and divide by the units to get cost per unit. Where asked, add profit to get the rate.
7Show a clear statement or table with heads of cost, amounts and the per-unit figure. State the answer with its unit.

Quickest way: Fast route for MCQs and written answers

When to use it: Use when time is short, especially in the 30 marks of MCQs and in short written parts of service costing.

For MCQs, check the unit in the options. If the options are in different units (per km vs per tonne-km), you can often drop two at once.
For absolute and commercial tonne-km, draw the trip as legs on one line: distance and load on each leg. This takes ten seconds and avoids errors.
Remember that an empty return leg adds nothing to absolute tonne-km. For commercial tonne-km, it adds its distance to the total distance and its zero load goes into the average load, which pulls the average down. Example: 10 tonnes out, empty back gives average load 5 tonnes.
Write costs in three columns: fixed, variable, semi-fixed. Place each item as you read it.
In written answers, start with a working note for units, then a cost statement, then the per-unit result. Step marks come from each working note, so do not skip them.

Common mistakes in Cost Units and Cost Classification in Service Sector

Mixing absolute and commercial tonne-km
Both use load and distance, and students apply one formula to every question.
Fix: Read the question for the word absolute or commercial. For absolute, sum load × distance leg by leg. For commercial, use average load × total distance.
Counting an empty return leg as loaded
Students multiply full load by the round-trip distance.
Fix: Take the load actually carried on each leg. An empty return leg has zero load, so add zero for it in absolute tonne-km.
Leaving the empty leg out of the average load for commercial tonne-km
Students compute the average on the loaded leg only, then multiply by the round-trip distance.
Fix: Include the zero load of the empty leg in the average. With 10 tonnes out and empty back, average load = (10 + 0) ÷ 2 = 5 tonnes, and commercial tonne-km = 5 × total distance.
Using available days when occupied days are needed, or the reverse
Bed-day and room-day look the same, so the difference is overlooked.
Fix: Underline occupancy in the question. Use occupied days for cost per occupied unit and available days only when the question asks for it.
Treating semi-fixed costs as wholly fixed or wholly variable
It is quicker to place the item in one column.
Fix: Split the cost into its fixed and variable parts using the data given, or use the high-low method if two activity levels are shown.
Mismatching periods for cost and units
Costs are given per year but units per month, or the reverse.
Fix: Convert everything to one period before dividing. Write the period at the top of your working.
Leaving the unit off the final answer
Students focus on the number.
Fix: Write the answer as ₹ per passenger-km, ₹ per tonne-km or ₹ per bed-day. The unit is part of the answer.

Worked examples

Example 1

A truck carries goods from Depot A to Depot B, 100 km away, with a load of 12 tonnes. It returns from B to A with a load of 8 tonnes. Find (a) absolute tonne-km and (b) commercial tonne-km for the round trip.

Show the solution

Leg 1: 12 tonnes × 100 km = 1,200 tonne-km.
Leg 2: 8 tonnes × 100 km = 800 tonne-km.
(a) Absolute tonne-km = 1,200 + 800 = 2,000.
Average load = (12 + 8) ÷ 2 = 10 tonnes.
Total distance = 100 + 100 = 200 km.
(b) Commercial tonne-km = 10 × 200 = 2,000.

Answer: Absolute tonne-km = 2,000 and commercial tonne-km = 2,000. They are equal here because both legs cover the same distance. When the legs cover equal distances, the two are equal even if the loads differ.

Example 2

A nursing home has 20 beds. In a 30-day month, 540 bed-days were occupied. Costs for the month: variable costs ₹1,08,000; fixed costs ₹90,000. Find (a) available bed-days, (b) occupancy percentage, (c) total cost per occupied bed-day.

Show the solution

(a) Available bed-days = 20 beds × 30 days = 600.
(b) Occupancy = 540 ÷ 600 × 100 = 90%.
Total cost = ₹1,08,000 + ₹90,000 = ₹1,98,000.
(c) Cost per occupied bed-day = ₹1,98,000 ÷ 540 = ₹366.67 (approx.).
Check: variable cost per occupied bed-day = ₹1,08,000 ÷ 540 = ₹200. Fixed cost per occupied bed-day = ₹90,000 ÷ 540 = ₹166.67. Sum = ₹366.67.

Answer: Available bed-days = 600; occupancy = 90%; cost per occupied bed-day = ₹366.67 approx. (₹200 variable + ₹166.67 fixed).

Exam tips

Draw the trip legs with load and distance before any calculation. It gives a clean working note and secures step marks.
Check whether the question wants available or occupied units. Hospital and hotel MCQs often turn on this single word.
When a cost is semi-fixed, show the split in a line of working. Even if the final figure is wrong, you earn marks for the method.
In an MCQ with several options close in value, recompute using the unit given rather than guessing from the nearest figure.
Always state the unit with your final answer, such as ₹ per tonne-km.

Practice questions from Service Costing

Cost Units and Cost Classification in Service Sector in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Cost Units and Cost Classification in Service Sector: frequently asked questions

What is a composite cost unit in service costing?

A composite cost unit combines two measures to describe a service, such as passenger-km (passengers × distance) or tonne-km (load × distance). Hospitals use bed-day and hotels use room-day in a similar way. It is used when one measure alone cannot show the service delivered.

What is the difference between absolute tonne-km and commercial tonne-km?

Absolute tonne-km is the sum of actual load × distance for each leg of the trip. Commercial tonne-km is the average load × the total distance travelled, and the average load includes any empty leg as zero. The two can differ when the legs cover different distances. With equal-distance legs they are equal even if the loads differ, so check which one the question asks for.

How are costs classified in service costing?

They are grouped as fixed, variable and semi-fixed. Fixed costs stay the same in the relevant range, such as insurance and rent. Variable costs move with activity, such as fuel. Semi-fixed costs have both a fixed and a variable part, and you split them using the data given.

Do I use available or occupied days for bed-day cost?

Use what the question asks for. Cost per occupied bed-day divides total cost by occupied days. Available bed-days are used to find occupancy. If the question is silent, state your assumption in the answer.