Cost Accounting · Operating Costing - Transport, Hotel and Healthcare

Absolute and Commercial Tonne-Km in Transport Costing

Updated 10 October 2026 · Fact-checked

Absolute tonne-km is the sum of each trip's load multiplied by its distance. Commercial tonne-km is the average load multiplied by the total distance, where average load is the mean of the load carried each way. Passenger-km is passengers multiplied by distance. Divide total cost by the unit to get cost per unit, then add profit to fix the rate.

Understand Transport Costing: Absolute and Commercial Units

Transport businesses sell movement, not a physical product. So you need a service unit to spread cost over. For goods transport the unit is the tonne-km. For passenger transport it is the passenger-km.

A tonne-km is one tonne carried for one kilometre. The problem is that loads change on each leg. A truck may carry 10 tonnes out and return empty. Two methods handle this.

Absolute tonne-km adds up the actual load times the actual distance for each leg. It is the real work done. An empty return leg adds zero.

Commercial tonne-km uses the average load. Take the simple mean of the loads carried on the legs, then multiply by the total distance travelled (all legs, including the empty return). It treats the whole round trip as one service. Because it uses the simple mean of the loads and not a distance-weighted figure, it differs from absolute tonne-km when the legs differ in distance. If the legs are equal in distance, the two match.

Do not confuse this with a distance-weighted average load (Σ load × distance ÷ total distance). That calculation simply gives back absolute tonne-km, so it is not the commercial method.

For passenger transport, passenger-km is the number of passengers carried times the distance. When you must estimate it for a period, use the effective passengers the vehicle can carry over the period, often at a stated capacity, and multiply by the km run. Exams usually give capacity and an occupancy percentage.

Once you have the cost for the period and the service unit, you get cost per unit. To fix a fare or freight rate, add the required profit, either as a percentage of cost or of the rate (sales).

Key rules to remember

Absolute tonne-km: Σ (load carried on each leg × distance of that leg); Empty legs contribute zero. Use the actual loads leg by leg.
Average load (commercial): Average load = (Sum of loads on the legs) ÷ (Number of legs); Use the simple mean of the loads, for example (load out + load back) ÷ 2. Do not weight by distance.
Commercial tonne-km: Average load × Total distance travelled (all legs); Total distance includes the empty return run. The result differs from absolute tonne-km when leg distances differ.
Passenger-km: Number of passengers × Distance travelled; For a period: passengers carried per trip × km per trip × number of trips. Use occupancy % of seating capacity if given.
Cost per unit: Total operating cost ÷ Total service units (tonne-km or passenger-km); Use the same unit basis for cost and for rate.
Rate with profit on cost: Rate per unit = Cost per unit + Profit % × Cost per unit; Profit as a percentage of cost.
Rate with profit on sales: Rate per unit = Cost per unit ÷ (1 − Profit % of sales); For example, 20% on sales means cost is 80% of the rate.

How to solve Transport Costing: Absolute and Commercial Units questions

Follow the same order for any transport costing question. Do the cost work and the unit work separately, then divide.

1Read the question and note the service unit asked: absolute tonne-km, commercial tonne-km or passenger-km.
2List each leg or trip with its load (or passengers) and distance. Mark empty legs clearly.
3Compute the units. For absolute: add load × distance for every leg. For commercial: find the simple mean of the loads, then multiply by total distance of all legs.
4Prepare the cost for the period, split into fixed (standing) and running costs. Convert annual or monthly figures to the period asked.
5Add the costs to get total cost. Include items like driver wages, fuel, depreciation, insurance, tax and repairs as given.
6Divide total cost by the units to get cost per unit.
7If a rate is asked, add profit on cost or on sales as stated.
8Write the final answer with units, such as ₹ per tonne-km, and show the working so you earn step marks.

Quickest way: Unit first, then divide

When to use it: Use this when time is short and the cost figures are already given for the period.

Write the trip table with load and distance in two columns.
Absolute: multiply across and total. Commercial: take the simple mean of the loads, then multiply by total km.
Total the costs once and divide by the units.
For profit on sales, divide by the cost percentage (for example ÷ 0.80), not by adding 20%.

Common mistakes in Transport Costing: Absolute and Commercial Units

Treating the empty return leg as zero distance in commercial tonne-km.
Students carry over the absolute method, where empty legs add nothing.
Fix: In commercial tonne-km, total distance includes the empty return. Only the average load reflects the empty run.
Averaging the load incorrectly, for example ignoring the empty leg.
Students take only the loaded load as the average.
Fix: Include every leg's load, including zero, when computing the simple mean.
Dividing cost by km instead of by tonne-km.
Both numbers appear in the table and look similar.
Fix: Check the unit asked. Cost per tonne-km needs the tonne-km figure as the divisor.
Adding 20% to cost when profit is 20% on sales.
Profit on cost and profit on sales look alike.
Fix: For profit on sales, rate = cost ÷ (1 − 0.20). Cost is 80% of the rate.
Not adjusting annual costs to the period asked.
Students rush to the unit calculation.
Fix: Convert every cost, such as insurance or road tax, to the same period as the units before adding.

Worked examples

Example 1

A truck runs from Pune to Nashik, 200 km, carrying 10 tonnes. It returns empty. Compute (a) absolute tonne-km and (b) commercial tonne-km for the round trip.

Show the solution

Leg 1: 10 tonnes × 200 km = 2,000 tonne-km.
Leg 2: 0 tonnes × 200 km = 0 tonne-km.
Absolute tonne-km = 2,000 + 0 = 2,000.
Average load = (10 + 0) ÷ 2 = 5 tonnes.
Total distance = 200 + 200 = 400 km.
Commercial tonne-km = 5 × 400 = 2,000.

Answer: Absolute tonne-km = 2,000. Commercial tonne-km = 2,000. They match here because both legs are the same distance. They would differ if the leg distances were different.

Example 2

A bus runs 50 km each way on a route, 4 round trips a day, for 25 days in a month. Seating capacity is 40 and average occupancy is 75%. Monthly total cost is ₹2,25,000. Find the passenger-km for the month, the cost per passenger-km, and the fare per passenger-km if profit is 20% on takings.

Show the solution

Assumption: the 75% average occupancy applies in both directions.
Passengers per trip = 40 × 75% = 30.
Km per day = 50 km × 2 (each way) × 4 round trips = 400 km.
Km per month = 400 × 25 = 10,000 km.
Passenger-km = 30 × 10,000 = 3,00,000.
Cost per passenger-km = ₹2,25,000 ÷ 3,00,000 = ₹0.75.
Profit is 20% on takings, so cost is 80% of the fare.
Fare per passenger-km = 0.75 ÷ 0.80 = ₹0.9375, about ₹0.94.

Answer: Passenger-km = 3,00,000 (assuming 75% occupancy in both directions). Cost = ₹0.75 per passenger-km. Fare = about ₹0.94 per passenger-km (₹0.9375).

Exam tips

Read whether the question wants absolute, commercial or both. Marks are given for each separately.
Set out a leg-wise table. Examiners award step marks for the table even if the final figure is wrong.
State your assumption when the question is unclear, such as how average load is taken or whether occupancy applies in both directions.
In the MCQ, look for the empty return trick and for profit on sales versus profit on cost.
Show cost per unit before adding profit, then show the rate on a separate line.

Practice questions from Operating Costing - Transport, Hotel and Healthcare

Transport Costing: Absolute and Commercial Units: frequently asked questions

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

Absolute tonne-km adds load × distance leg by leg, so empty legs count as zero. Commercial tonne-km uses the simple mean of the loads multiplied by the total distance of all legs. The two differ when the leg distances differ, and match when the legs are equal in distance.

How do I calculate passenger-km in operating costing?

Multiply the number of passengers by the distance. For a period, find passengers per trip from capacity and occupancy, then multiply by total km run in the period.

Which unit should I use to find cost per unit?

Use the unit the question names. For goods it is usually tonne-km, absolute or commercial. For passenger vehicles it is passenger-km.

How do I fix a fare with a profit margin?

Find cost per unit first. If profit is a percentage of cost, add that percentage to the cost. If profit is a percentage of takings, divide the cost by (1 minus the profit percentage).