Overhead Allocation Rate Calculator
Build a predetermined overhead rate from a budgeted indirect-cost pool and activity driver. Route that rate to a job, compare applied with actual overhead, expose under- or overapplication, and test practical-capacity and alternative-driver rates before relying on one unit cost.
Set the cost pool and route
The default driver is described generically so it can represent machine hours, labor hours, or another activity. Label the driver in the costing system and do not combine unlike units in one denominator.
The allocation route
The job consumes 120 driver units and receives $3,600 of overhead. This route should be traceable from budget through shop-floor or service activity to the cost record, with no driver units lost or counted twice.
Overhead allocation formulas
Predetermined overhead rate = budgeted indirect cost pool / budgeted driver activity
Applied overhead = predetermined rate x actual driver activity
Under- or overapplied overhead = actual overhead - applied overhead
Job cost = direct materials + direct labor + job driver units x predetermined rate
Practical-capacity rate = budgeted overhead / practical-capacity driver units
A positive reconciliation balance is underapplied because actual overhead exceeds applied overhead. A negative balance is overapplied. Financial-statement disposition can use COGS adjustment, proration, or another policy under the applicable framework and materiality.
Worked factory-routing example
The plant budgets $1.2 million of indirect manufacturing overhead and 40,000 machine hours. The predetermined rate is $30 per machine hour. Actual activity is 38,000 hours, so the system applies $1.14 million. Actual overhead is $1.25 million, leaving $110,000 underapplied and only 91.2 percent of actual overhead covered by the rate.
A job uses 120 machine hours, so it receives $3,600 of overhead. Direct materials are $8,000 and direct labor is $6,000, producing a $17,600 job cost. Across 200 good units, modeled unit cost is $88, and overhead is 20.45 percent of job cost.
Actual overhead divided by actual activity is $32.89 per hour, $2.89 above the predetermined rate. If the pool were divided by 50,000 practical-capacity hours, the rate would be $24 and the gap between practical and budgeted activity would represent $240,000 of modeled unused-capacity cost. That capacity view avoids forcing every idle-cost dollar into the units expected to be produced.
Build a homogeneous indirect-cost pool
Production support
Supervision, maintenance, factory utilities, depreciation, quality, and indirect supplies may share production-related drivers.
Purchasing and setups
Purchase orders, receipts, setups, inspections, and batches can be driven by transactions rather than machine or labor hours.
Facility and administration
Square feet, headcount, labor dollars, transactions, or direct cost can fit different facility and support services.
Costs inside one pool should respond similarly to the chosen driver. If setup cost follows batches while power follows machine hours, one blended rate can subsidize high-setup products with high-volume products. Activity-based costing separates pools when the decision benefit exceeds complexity.
Choose a driver that reflects cause or benefit
Machine hours can suit automated production; direct labor hours can suit labor-intensive work; labor dollars may fit payroll-related support; setups can fit batch support; square feet can fit occupancy. A convenient driver is not necessarily an explanatory driver.
Test correlation, operational logic, data quality, manipulation risk, volatility, and cost of collection. Drivers should be measured consistently across jobs and periods. Planned units and actual units need the same definition, including downtime, rework, scrap, and subcontracted work.
The alternative rate of $20 per alternative driver unit is not directly comparable with $30 per machine hour because the units differ. Apply each driver to representative jobs before selecting a policy.
Denominator capacity changes product cost
Dividing fixed overhead by expected low volume raises the unit rate and can make products appear uncompetitive, potentially reducing volume further. Dividing by unrealistic theoretical capacity can underallocate cost. Practical capacity generally reflects attainable output after normal maintenance, setup, breaks, and unavoidable interruptions.
Separate cost of idle capacity for management visibility when the framework permits. The default practical-capacity rate is $24, while the budgeted-activity rate is $30. The $6 difference across 40,000 planned hours identifies $240,000 linked to the 10,000-hour practical-capacity gap.
Tax inventory, U.S. GAAP inventory, government contracts, pricing, and internal decisions may require different denominator rules. Maintain reconciliations instead of forcing one rate to serve every purpose.
Underapplication can come from cost, volume, or both
The default underapplication reflects actual overhead $50,000 above budget and actual activity 2,000 units below plan. At the predetermined rate, the volume shortfall applies $60,000 less than planned. Together they produce a $110,000 gap.
Analyze spending by account, rate, quantity, efficiency, capacity, timing, and classification. Utilities, maintenance events, salary changes, depreciation, property tax, repairs, insurance, and production volume may explain different portions. A single reconciliation number is a control signal, not a diagnosis.
Close the variance according to documented policy and materiality. Do not change the job rate retroactively solely to make the balance disappear unless the accounting method calls for an actual-rate adjustment.
Allocated job cost is not incremental cash cost
The $3,600 overhead allocation helps price and evaluate the job within the full operating structure. If the plant has idle capacity, accepting one more job may not create all $3,600 of cash outflow. Conversely, a large order can trigger overtime, maintenance, outsourcing, or a capacity expansion not represented by the average rate.
For short-run decisions, compare incremental revenue with direct and avoidable costs, opportunity cost, bottlenecks, and risk. For long-run sustainability, ensure the portfolio covers shared infrastructure and target return.
Report direct cost, variable overhead, fixed overhead allocation, and contribution separately when decision makers might confuse average full cost with marginal cost.
Service businesses also need indirect-cost routes
Consulting, health care, construction, logistics, agencies, software services, laboratories, and nonprofits can allocate support labor, facilities, technology, insurance, administration, and compliance to engagements, grants, contracts, departments, or service lines.
Billable labor hours may allocate overhead, but utilization can create the same denominator problem as factory capacity. Headcount, cases, transactions, visits, compute usage, square feet, or direct labor dollars may be more appropriate for some pools.
Government awards and contracts can impose allowability, allocability, consistency, indirect-rate, and documentation requirements. Federal Acquisition Regulation 31.203 addresses indirect costs for covered contracts; specific agencies and agreements add requirements.
Tax inventory and management allocation can differ
IRS Publication 334 describes certain overhead that may enter COGS for manufacturers, while Internal Revenue Code section 263A and related rules can require capitalization of direct and indirect costs for covered taxpayers. Exceptions and small-business rules depend on facts and current thresholds.
This calculator does not decide which accounts are capitalizable, deductible, production-related, or allocable for tax.
Preserve the chart-of-accounts map, pool membership, driver support, capacity rationale, applied-overhead records, variance analysis, and book-to-tax reconciliation.
Review rates before and after the period
Before the period, approve budget, pools, drivers, capacity, rates, and job-master configuration. During the period, monitor driver capture and material cost changes. After the period, reconcile actual overhead and activity, analyze variance, and update forward rates without erasing history.
Version rates with effective dates. A midyear acquisition, facility opening, automation project, volume collapse, or reorganization may justify a prospective revision. Explain the impact on product, customer, and department profitability.
Test allocations for cross-subsidy. Products that consume many setups, inspections, engineering changes, rush orders, or support incidents can be undercosted by a volume-only driver.
Overhead-rate control checklist
- Define direct versus indirect cost.
- Create homogeneous cost pools.
- Select causal or beneficial drivers.
- Choose a capacity denominator.
- Budget pool and activity together.
- Version the approved rate.
- Capture job driver units accurately.
- Reconcile applied to actual overhead.
- Analyze spending and volume variance.
- Separate full from incremental cost.
- Meet tax and contract rules.
- Test cross-subsidy by product.
Frequently asked questions
How do I calculate an overhead allocation rate?
Divide a defined budgeted indirect-cost pool by budgeted activity for the selected driver, then multiply the rate by each job’s driver use.
What is underapplied overhead?
Actual overhead exceeds overhead applied to production or jobs. It can reflect higher spending, lower activity, or both.
Should I use actual or budgeted activity?
A predetermined rate normally uses budgeted cost and activity. Actual figures reconcile the period and identify variance.
Why show practical capacity?
It can separate unused-capacity cost and reduce the circular effect of loading fixed overhead onto fewer expected units.
Is allocated overhead the cost of accepting one more job?
Not necessarily. Short-run incremental cost depends on avoidable resources, bottlenecks, capacity, and opportunity cost.