Activity-based costing: rates and product decisions
For each activity, divide its cost pool by total driver units, then multiply that rate by the product’s driver use. Add the assigned activity costs only after computing every pool. ABC explains resource consumption; it does not by itself establish avoidable cost.
ABC in three calculations
- Activity rate
- Cost pool ÷ total driver units.
- Assigned overhead
- Activity rate × product driver use, summed across all pools.
- Overhead per product unit
- Total assigned overhead ÷ product units.
A setup, inspection and machine-hour are different driver units. Calculate each pool separately.
See the decision
Two activity pools, one product
Setup cost is $72,000 for 240 setups; inspection cost is $48,000 for 600 inspections. Product A uses 30 setups and 100 inspections and produces 2,000 units. All drivers are comparable within their pool.
USD allocated overhead
- Setups$9,000
- Inspections$8,000
Assign $8.50 of overhead per Product A unit. Add direct costs separately; do not call the full $17,000 an avoidable cash saving.
How to apply these ideas
1. Define pools
Keep activities with different cost drivers separate.
Setup work and inspections need not move with production units. Combining them into one pool can recreate the cross-subsidy that ABC is meant to reveal. Define the period, cost pool and practical driver before calculating a rate.
Watch for: Using direct labor hours for every support activity.
2. Compute rates
Activity rate = pool cost ÷ total driver quantity.
Use the driver quantity for the same period and population as the cost pool. Label the unit, such as dollars per setup, so you cannot multiply a setup rate by production units accidentally.
Watch for: Dividing by only one product’s driver usage.
3. Assign costs
Product assignment = rate × product driver use.
Calculate the assignment from each pool, then sum. For a per-unit product cost, divide the product’s total assignment by its own output. Reconcile the full set of products to the pool under the chosen capacity convention.
Watch for: Reporting the total assignment as cost per unit.
4. Use the result
Investigate product complexity before making a pricing or discontinuation decision.
A low-volume product may consume many setups and inspections. That finding can motivate batch changes or pricing review. Dropping it saves cash only when resources are avoidable or freed capacity has an alternative use.
Watch for: Assuming allocated overhead disappears if the product is dropped.
Study the topic
Activity-based costing: rates and product decisions: explanations and applications
Calculate activity rates, reconcile product assignments and compare ABC with a broad allocation base. Cost management remains the parent for costing systems and inventory measurement.
By MiloPrep editorial team. Original teaching explanations and illustrative cases; official curriculum references are listed below.
Choose drivers that describe the work being done
Unit-level activity follows individual output, such as machine time. Batch-level activity follows production runs, such as setup. Product-sustaining work supports a product regardless of the number of units or batches. Facility-level activity supports the operation more broadly. A unit-volume base can misassign batch or product complexity when products use those activities differently.
Define the pool before choosing a driver. A setup count assumes setups consume comparable resources; if one setup takes ten times longer, setup-hours may be more causal. The cost of gathering a more detailed driver should be weighed against the quality of decisions it enables, but a conveniently available measure should not be mistaken for evidence of causation.
| Pool | Possible driver | Check before using it |
|---|---|---|
| Machine support | Machine-hours | Similar support demand per hour |
| Setups | Setup count or setup-hours | Variation in setup complexity |
| Inspection | Inspection-hours or comparable inspections | Scope and effort of each inspection |
| Product engineering | Engineering-hours or change orders | Comparable work content |
| Facility support | Explicit policy or separate reporting | Avoid pretending every cost has a product-level causal driver |
Compare the same total pool under both methods
A fair ABC comparison holds the cost pool, period and production facts constant. First compute the broad rate and assign the full pool. Then compute separate activity rates and assign each pool using the appropriate driver. Reconcile each method to the same total, unless the model explicitly identifies unused capacity or unassigned facility costs.
The change in product assignment explains cross-subsidy under the chosen drivers. A high-volume simple product may lose cost under ABC while a low-volume complex product gains it. The result is a reason to inspect batch sizes, design and pricing. It does not prove that either product should be discontinued or that the reassigned amount can be saved in cash.
Convert an allocation finding into an operational decision
A capacity-based activity rate can separate supplied capacity from capacity used. If resources cost $60,000 and practical capacity is 3,000 hours, the rate is $20 per hour. Using only 2,400 hours assigns $48,000 to usage and identifies $12,000 of unused capacity. Dividing by actual usage instead would load the idle-capacity cost into the work performed.
Before promising savings, identify how resources would change. Fewer setups may free time without reducing salaried payroll immediately. That time has value if it supports another useful activity, or if a future commitment can be avoided. State the time horizon, resource adjustment and alternative use separately from the accounting assignment.
Work it through
Worked example: Two activity pools, one product
Setup cost is $72,000 for 240 setups; inspection cost is $48,000 for 600 inspections. Product A uses 30 setups and 100 inspections and produces 2,000 units. All drivers are comparable within their pool.
| Activity | Rate | Product A use | Assigned cost |
|---|---|---|---|
| Setup | $300/setup | 30 | $9,000 |
| Inspection | $80/inspection | 100 | $8,000 |
| Total | Not applicable | Not applicable | $17,000 |
- 1
Setup rate = 72,000 / 240 = $300; inspection rate = 48,000 / 600 = $80.
- 2
Product A overhead = 30 × 300 + 100 × 80 = $17,000; per unit = 17,000 / 2,000 = $8.50.
Assign $8.50 of overhead per Product A unit. Add direct costs separately; do not call the full $17,000 an avoidable cash saving.
Work through the alternatives
More worked cases: activity-based costing: rates and product decisions
Original teaching scenarios. Each case states its assumptions, shows the working and explains the limits of the conclusion.
Two products reveal a batch-cost cross-subsidy
Overhead is $100,000: $60,000 setups and $40,000 machine support. A makes 8,000 units using 20 setups and 3,000 machine-hours. B makes 2,000 units using 80 setups and 1,000 machine-hours. Compare a plantwide machine-hour rate with ABC.
| Product | Plantwide overhead | ABC overhead | ABC per unit |
|---|---|---|---|
| A | $75,000 | $42,000 | $5.25 |
| B | $25,000 | $58,000 | $29.00 |
| Total | $100,000 | $100,000 | Not additive |
- Plantwide rate = 100,000/4,000 = $25 per machine-hour. A receives $75,000 and B $25,000.
- ABC setup rate = 60,000/100 = $600; machine rate = 40,000/4,000 = $10. A receives 20 × 600 + 3,000 × 10 = $42,000; B receives $58,000.
- Divide by each product’s own output: A $42,000/8,000 = $5.25 and B $58,000/2,000 = $29.00.
What the result means: B consumes 80% of setups but only 25% of machine-hours. The broad rate obscures that batch intensity; ABC does not change the $100,000 total spending.
Practice this topic
Check your understanding
Try each short application before opening its explanation. These are original learning checks, not official exam questions or a score prediction.
1. A support pool costs $72,000 with practical capacity of 4,000 hours. Products use 3,500 hours. How much cost is unused capacity under this model?
Show answer and explanation
$9,000.
The rate is $18 per practical-capacity hour. Assign $63,000 to usage; the remaining 500 hours cost $9,000.
2. ABC assigns $25,000 more overhead to a product. Does eliminating the product necessarily save $25,000?
Show answer and explanation
No.
Determine which resources can be removed or used elsewhere. Assignment and avoidability answer different questions.
Questions about activity-based costing: rates and product decisions
- Can ABC change total company overhead?
- Changing the assignment method redistributes the same pool under the stated assumptions. Cash savings require an operational change, not a new allocation label.
- Does low volume always mean high unit overhead?
- No. Driver consumption matters. A low-volume product with few support activities may use less overhead than a high-volume but complex product.
Sources and scope
Curriculum mapping: Part 1, Section D, Cost Management. The official outline assigns 15% to the entire domain, not to this individual technique. These are selected study notes, not complete curriculum coverage.
Official curriculum references establish scope and expected skills. The explanations, diagrams and numerical cases are independent teaching material from MiloPrep, not official questions or source-validated solutions. Curriculum references checked 2026-10-10.
- IMA Content Specification Outlines (effective September 2024) ↗
Supports: Part 1, Section D, beginning on printed page 7. Domain names, weights and curriculum boundaries.
- IMA Learning Outcome Statements (effective September 2024) ↗
Supports: Part 1 D.2.g-h and D.3.m: ABC assignment; printed page 10. Curriculum scope, not verification of this original worked example.
Independent US CMA study material. Not affiliated with or endorsed by IMA. This covers management accounting, not medical-assistant certification or the separate ICMAI qualification.