Accountants Overhead Cost Formula
Learn how to calculate an accounting practice's monthly and annual overhead and the overhead cost to recover per billable hour.
This calculation estimates the recurring cost of running an accounting practice and spreads that cost across realistic billable capacity. It helps separate the overhead portion of an hourly fee from direct delivery costs and profit.
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Overhead Cost per Billable Hour
Where:
Add recurring monthly practice costs, calculate the team's expected billable hours, then divide costs by hours. The result is the overhead amount that each billable hour needs to recover.
Variables Explained
| Variable | What It Means | Unit |
|---|---|---|
| monthlyOverhead - Total monthly overhead | The combined recurring monthly cost of rent, support payroll, technology, professional fees, insurance, and other operating costs. | currency |
| monthlyBillableHours - Total monthly billable hours | The expected client-chargeable hours available from all billable accountants during one month. | hours |
| officeRent - Monthly office rent | Rent, service charges, and regular workspace costs. | currency |
| supportPayroll - Monthly support and admin payroll | Pay, employer costs, and benefits for non-billable support and administrative roles. | currency |
| accountingSoftware - Monthly software and technology | Costs for accounting platforms, cloud storage, IT support, and subscriptions. | currency |
| professionalFees - Monthly professional fees and insurance | Professional indemnity insurance, memberships, legal, and compliance costs. | currency |
| otherOverheads - Other monthly overheads | Other recurring costs such as utilities, marketing, travel, training, and supplies. | currency |
| billableAccountants - Number of billable accountants | The number of team members expected to generate billable client work. | number |
| billableHoursPerAccountant - Billable hours per accountant per month | Realistic client-chargeable hours per billable accountant after non-billable time. | hours |
Step-by-Step Calculation
Add the recurring monthly costs
Combine the regular operating costs entered for the practice.
monthlyOverhead = officeRent + supportPayroll + accountingSoftware + professionalFees + otherOverheads
Project annual overhead
Multiply the monthly estimate by 12 to show an annual run-rate.
annualOverhead = monthlyOverhead * 12
Calculate team billable capacity
Multiply the number of billable accountants by the realistic monthly billable hours for each person.
monthlyBillableHours = billableAccountants * billableHoursPerAccountant
Project annual billable capacity
Multiply monthly billable capacity by 12 for a yearly capacity estimate.
annualBillableHours = monthlyBillableHours * 12
Calculate overhead per billable hour
Divide monthly overhead by monthly billable capacity. This gives the hourly overhead recovery amount before direct billable staff costs, profit, or taxes.
overheadCostPerHour = monthlyOverhead / monthlyBillableHours
Example: Small accounting practice overhead recovery
Add monthly overheads
2500 + 12000 + 1000 + 750 + 750
$17,000
Calculate annual overhead
17000 * 12
$204,000
Calculate monthly billable capacity
4 * 100
400 hours
Calculate annual billable capacity
400 * 12
4,800 hours
Calculate overhead per billable hour
17000 / 400
$42.50 per hour
Final Result
The practice has estimated monthly overhead of $17,000, annual overhead of $204,000, and an overhead recovery requirement of $42.50 per billable hour.
Assumptions
- ✓All entered operating costs are recurring monthly costs.
- ✓Billable hours reflect client-chargeable work rather than total contracted or working hours.
- ✓Each billable accountant is assumed to have the same expected monthly billable hours.
- ✓Annual overhead and annual billable capacity are estimated by multiplying monthly figures by 12.
- ✓The hourly result includes overhead only, unless direct billable staff costs have deliberately been entered as overhead.
Limitations
- !Actual costs can change during the year because of hiring, lease changes, subscription renewals, inflation, or unexpected expenses.
- !Billable capacity can be lower than planned due to leave, internal work, delayed projects, write-offs, or demand changes.
- !The calculation does not set a final charge-out rate because it excludes direct delivery costs, profit targets, and taxes unless included in inputs.
- !A single average hourly figure may not reflect different teams, service lines, seniority levels, or engagement types.
Common Mistakes to Avoid
Using total working hours instead of realistic billable client hours.
Leaving out employer costs and benefits for support staff.
Treating the overhead cost per hour as the final client billing rate.
Including one-off expenses as though they recur every month without adjusting the estimate.
Counting billable accountants who have little or no client-chargeable capacity.
Forgetting remote-work, software, insurance, marketing, or compliance costs.
Related Formulas
Frequently Asked Questions
What is the formula for accounting practice overhead cost per hour?
Divide total monthly overhead by total monthly billable hours. Total monthly billable hours equal the number of billable accountants multiplied by expected billable hours per accountant.
How do I calculate total monthly overhead for an accounting firm?
Add recurring costs such as office space, non-billable payroll, technology, professional fees, insurance, and other operating expenses.
Why are billable hours used in the overhead formula?
Billable hours are the capacity through which the practice earns client revenue. Spreading overhead across those hours produces an hourly recovery estimate.
Does overhead per billable hour include accountant salaries?
It includes them only if they are entered in the cost inputs. This calculator is commonly used with support payroll as overhead while direct billable staff costs are added separately when pricing work.
How is annual overhead calculated?
The estimate multiplies total monthly overhead by 12. It is a run-rate estimate and may differ if costs vary through the year.
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