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Performance Management · Activity-based costing

How to Calculate Product Costs Using ABC

Updated 11 October 2026 · Fact-checked

Activity-based costing (ABC) groups overheads into cost pools, divides each pool by its cost driver volume to get an activity rate, then charges each product with rate × the driver units it uses. Add direct costs and divide by units produced to get the unit cost.

Understand Calculating Product Costs Using ABC

Traditional absorption costing spreads all overheads over products using one base, usually direct labour hours or machine hours. This works when overheads really do move with that base. In modern firms many overheads do not. Set-ups, inspections, ordering and deliveries depend on how many times an activity happens, not on how long a machine runs.

ABC fixes this by tracing overheads to the activities that cause them. Each activity has a cost pool (the overhead cost of that activity) and a cost driver (the thing that makes the cost rise, such as number of set-ups). You divide the pool by the total driver volume to get a rate per driver unit.

Each product then takes a share of each pool according to how much of the driver it uses. A low-volume, complex product may need many set-ups and inspections for few units. ABC gives it a high overhead cost per unit. Traditional costing hides this and spreads the cost onto high-volume, simple products.

The total overhead absorbed is the same under both methods. Only the split between products changes. So ABC shifts profit between products, not in total (unless closing inventory differs from opening inventory). This is the key point for comparison questions.

Key rules to remember

Activity absorption rate
Activity rate = Cost pool ÷ Total cost driver volume
Use the total driver volume for all products, not for one product.
Overhead charged to a product
Overhead for product = Σ (activity rate × driver units used by the product)
Add the charge from every activity pool.
ABC overhead per unit
Overhead per unit = Total overhead charged to product ÷ Units produced
Divide by units of that product, not total units.
Full ABC unit cost
Unit cost = Direct materials + Direct labour + ABC overhead per unit
Direct costs are traced as normal in both methods.
Traditional absorption rate
Rate = Total overheads ÷ Total absorption base (e.g. machine hours)
Used as the comparison. Total overhead absorbed must equal total under ABC.

How to solve Calculating Product Costs Using ABC questions

This method works for any ABC product costing question. Lay it out in a table so you can check totals.

  1. 1List each overhead cost pool and its cost driver. Check the total of the pools.
  2. 2Total the driver volumes across all products for each activity.
  3. 3Calculate each activity rate: pool ÷ total driver volume.
  4. 4For each product, multiply each rate by the driver units that product uses. Add these to get total overhead per product.
  5. 5Check that the product overheads add up to the total of the pools.
  6. 6Divide by units produced to get overhead per unit. Add direct costs to get the full unit cost.
  7. 7If asked, calculate the traditional cost using one absorption base, then compare unit costs and profit per product.
  8. 8Comment: say which products were over- or under-costed and what this means for pricing and product decisions.

Quickest way: Table method with a total check

When to use it: Use this for Section C numerical parts and for OT cases where you need a unit cost fast.

  1. Draw one row per activity and one column per product plus a total column.
  2. Write the driver volumes in the table. The total column gives the divisor for each rate.
  3. Compute the rate and multiply down each product column. Use the calculator memory for long sums.
  4. Add each product column. The sum must equal total overheads. If it does not, find the error before moving on.
  5. Divide by units and add direct cost per unit. For OT questions, check which figure is asked for: total, per unit or profit.

Common mistakes in Calculating Product Costs Using ABC

  • Dividing a cost pool by one product's driver volume instead of the total volume.

    Students rush to the product they are asked about.

    Fix: Always calculate the rate from total driver volume first. Then apply it to each product.

  • Forgetting to divide by units produced at the end.

    The overhead charged to a product is a total, and students treat it as a unit figure.

    Fix: Label every figure as total or per unit. Divide the product's total overhead by its own units.

  • Leaving out direct costs when asked for full unit cost or profit.

    The question focuses on overheads, so direct costs are forgotten.

    Fix: Read the last line of the requirement. If it says cost per unit or profit, add direct costs.

  • Choosing a poor cost driver, such as machine hours for an ordering cost.

    Students default to the usual absorption base.

    Fix: Ask what makes the cost rise. Ordering cost rises with number of orders, so use orders.

  • Saying ABC changes total profit.

    Unit costs change, so students assume profit changes too.

    Fix: Total overhead absorbed is the same. Profit differs only by product, or in total if inventory changes.

  • Giving a numerical answer with no comment when the requirement says discuss.

    Students stop once the calculation is done.

    Fix: Add two or three points: which product was cross-subsidised, what the new costs mean for pricing, and a limitation of ABC.

Worked examples

Example 1

A company makes products A and B. Overheads are: set-up costs $120,000 (driver: number of set-ups), inspection costs $90,000 (driver: number of inspections) and machining costs $200,000 (driver: machine hours). Data: A: 10,000 units, 20 set-ups, 40 inspections, 20,000 machine hours, direct cost $30 per unit. B: 2,000 units, 40 set-ups, 50 inspections, 5,000 machine hours, direct cost $50 per unit. Selling prices are A $70 and B $120. Calculate the full unit cost and profit of each product using ABC and using traditional absorption costing on machine hours.

Show the solution
  1. Total driver volumes: set-ups 20 + 40 = 60; inspections 40 + 50 = 90; machine hours 20,000 + 5,000 = 25,000.
  2. Activity rates: set-ups $120,000 ÷ 60 = $2,000 each; inspections $90,000 ÷ 90 = $1,000 each; machining $200,000 ÷ 25,000 = $8 per hour.
  3. Product A overhead: (20 × 2,000) + (40 × 1,000) + (20,000 × 8) = 40,000 + 40,000 + 160,000 = $240,000. Per unit: $240,000 ÷ 10,000 = $24.
  4. Product B overhead: (40 × 2,000) + (50 × 1,000) + (5,000 × 8) = 80,000 + 50,000 + 40,000 = $170,000. Per unit: $170,000 ÷ 2,000 = $85.
  5. Check: $240,000 + $170,000 = $410,000 = total overheads.
  6. ABC full unit cost: A $30 + $24 = $54; B $50 + $85 = $135.
  7. Traditional rate: $410,000 ÷ 25,000 = $16.40 per machine hour. A overhead: 20,000 × 16.40 = $328,000, or $32.80 per unit. B overhead: 5,000 × 16.40 = $82,000, or $41 per unit.
  8. Traditional full unit cost: A $30 + $32.80 = $62.80; B $50 + $41 = $91.
  9. Profit per unit under ABC: A $70 − $54 = $16; B $120 − $135 = −$15. Total: A $160,000, B −$30,000, so $130,000.
  10. Profit per unit under traditional: A $70 − $62.80 = $7.20; B $120 − $91 = $29. Total: A $72,000, B $58,000, so $130,000.

Answer: ABC full unit cost: A $54, B $135. Traditional: A $62.80, B $91. ABC profit: A $160,000, B loss of $30,000. Traditional profit: A $72,000, B $58,000. Total profit is $130,000 under both. Traditional costing over-costs A and under-costs B, because B uses few machine hours but many set-ups and inspections.

Example 2

A firm makes 9,500 standard units and 500 bespoke units. Overheads are: ordering $60,000 (driver: purchase orders), delivery $45,000 (driver: deliveries) and assembly $90,000 (driver: direct labour hours). Standard: 100 orders, 100 deliveries, 6,000 labour hours. Bespoke: 200 orders, 200 deliveries, 3,000 labour hours. Calculate the ABC overhead per unit for each product. Compare with a traditional overhead per unit if overheads are spread equally over all 10,000 units, and comment.

Show the solution
  1. Total drivers: orders 100 + 200 = 300; deliveries 100 + 200 = 300; labour hours 6,000 + 3,000 = 9,000.
  2. Rates: ordering $60,000 ÷ 300 = $200 per order; delivery $45,000 ÷ 300 = $150 per delivery; assembly $90,000 ÷ 9,000 = $10 per hour.
  3. Standard overhead: (100 × 200) + (100 × 150) + (6,000 × 10) = 20,000 + 15,000 + 60,000 = $95,000. Per unit: $95,000 ÷ 9,500 = $10.
  4. Bespoke overhead: (200 × 200) + (200 × 150) + (3,000 × 10) = 40,000 + 30,000 + 30,000 = $100,000. Per unit: $100,000 ÷ 500 = $200.
  5. Check: $95,000 + $100,000 = $195,000 = $60,000 + $45,000 + $90,000.
  6. Traditional per unit: $195,000 ÷ 10,000 = $19.50 for both products.
  7. Comment: the traditional method over-costs standard units by $9.50 and under-costs bespoke units by $180.50 per unit.

Answer: ABC overhead per unit: standard $10, bespoke $200. Traditional: $19.50 for each. Bespoke units use many orders and deliveries for few units, so the traditional method subsidises them at the expense of standard units. If prices were set from traditional costs, bespoke work could be priced too low and standard units too high, which could harm competitiveness.

Exam tips

  • Always show the activity rate calculation. Marks are given for the method even if one number is wrong.
  • Do the total check on overheads before moving on. It catches most arithmetic and driver errors.
  • In OT questions, read what is asked: rate, overhead per unit, full unit cost or profit. Options are often built from the common wrong steps, such as not dividing by units.
  • For discussion parts, link the numbers to a decision: pricing, product mix or dropping a product. Add one limitation, such as the cost of collecting driver data.
  • If a question gives the traditional method, compute it with the same total overheads so both methods reconcile.

Practice questions from Activity-based costing

Calculating Product Costs Using ABC in other exams

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

Calculating Product Costs Using ABC: frequently asked questions

How do you calculate the cost per unit using ABC?

Calculate an activity rate for each pool by dividing the pool by total driver volume. Multiply each rate by the driver units a product uses and add the results. Divide by units produced and add direct costs per unit.

Does ABC change total profit compared with absorption costing?

Not if all overhead is charged to the period's output and inventory does not change. The total overhead absorbed is the same and only its split between products changes. Profit can differ in total if inventory levels change, because each method defers a different amount of overhead.

Which products usually cost more under ABC?

Low-volume, complex products that use many activities such as set-ups, inspections and deliveries. Traditional costing spreads these costs onto high-volume products, so it tends to over-cost simple, high-volume ones.

What is the difference between a cost pool and a cost driver?

A cost pool is the total overhead cost of an activity. A cost driver is the measure that causes that cost to rise, such as number of set-ups. You divide the pool by the driver volume to get the rate.