Accountants Overhead Cost Per Billable Hour Formula
Learn how to calculate an accounting firm's annual overhead, hourly overhead cost, and overhead allocation per accountant.
An overhead cost per billable hour shows how much of a firm's operating cost must be recovered by each client-invoiced hour. It provides a cost-recovery baseline for capacity planning and pricing, before direct delivery costs, profit, and taxes are considered.
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Overhead Cost Per Billable Hour
Where:
Add all annual operating overheads, then divide the total by the number of hours the firm realistically expects to invoice to clients.
Variables Explained
| Variable | What It Means | Unit |
|---|---|---|
| annualOfficeCosts - Annual office costs | Annual premises and office running costs, such as rent, utilities, cleaning, rates, and supplies. | currency |
| annualSoftwareCosts - Annual software and technology costs | Annual costs for accounting software, cloud tools, IT support, phones, and equipment. | currency |
| annualAdminCosts - Annual administration costs | Annual non-billable administration and support costs. | currency |
| annualProfessionalCosts - Annual professional costs | Annual insurance, memberships, training, compliance, and legal costs. | currency |
| otherAnnualOverheads - Other annual overheads | Other recurring operating costs, such as marketing, bank charges, or depreciation. | currency |
| annualBillableHours - Expected annual billable hours | Combined client hours the firm expects to invoice during the year. | hours |
| numberOfAccountants - Number of accountants | Number of fee-earning accountants used for the equal-share annual allocation. | number |
Step-by-Step Calculation
Add annual office costs
Combine premises-related expenses with technology and software costs.
officeAndTechnologyCosts = annualOfficeCosts + annualSoftwareCosts
Add people and professional overheads
Combine non-billable administration with professional operating costs.
supportAndProfessionalCosts = annualAdminCosts + annualProfessionalCosts
Calculate total annual overhead
This is the firm's total recurring annual operating overhead.
annualOverhead = officeAndTechnologyCosts + supportAndProfessionalCosts + otherAnnualOverheads
Calculate hourly overhead cost
Spread total overhead across expected invoiced client hours.
hourlyOverheadCost = annualOverhead / annualBillableHours
Calculate annual overhead per accountant
Allocate annual overhead equally across the entered fee-earning accountants.
overheadPerAccountant = annualOverhead / numberOfAccountants
Worked example: five-person accounting practice
Combine office and technology costs
£24,000 + £12,000
£36,000
Combine administration and professional costs
£35,000 + £9,000
£44,000
Calculate total annual overhead
£36,000 + £44,000 + £10,000
£90,000
Calculate hourly overhead cost
£90,000 ÷ 3,600
£25.00 per billable hour
Calculate overhead per accountant
£90,000 ÷ 5
£18,000 per accountant per year
Final Result
The practice has estimated annual overhead of £90,000, equal to £25.00 per billable hour and £18,000 per accountant per year.
Assumptions
- ✓All entered amounts are annual recurring operating overheads in the same currency.
- ✓Expected billable hours represent invoiced client work rather than total working hours.
- ✓Overhead is spread evenly across all expected annual billable hours.
- ✓The allocation per accountant is an equal-share figure rather than an individual cost measure.
Limitations
- !Actual billable hours can differ from forecasts because of leave, training, internal work, and changes in demand.
- !Costs may change during the year, particularly rent, software subscriptions, staffing, and marketing costs.
- !The hourly result does not include fee-earner pay unless it is entered within an overhead category.
- !The result is a cost-allocation estimate, not a recommended client charge-out rate.
Common Mistakes to Avoid
Using total working hours instead of hours that can actually be invoiced to clients.
Leaving out recurring costs such as insurance, software renewals, support staff costs, or compliance fees.
Including one-off capital purchases as though they were normal annual overheads without using a consistent annual allocation.
Treating the hourly overhead figure as a final fee rate without considering direct labour, client-specific costs, and profit.
Dividing by the number of accountants instead of billable hours when calculating the hourly figure.
Related Formulas
Frequently Asked Questions
How do you calculate overhead cost per billable hour for an accounting firm?
Add annual operating overheads and divide the total by realistic annual billable hours. The result is the overhead amount allocated to each invoiced hour.
What is included in accounting firm overhead?
Common categories include premises, software, IT, non-billable administration, insurance, professional memberships, training, compliance, marketing, and office supplies.
Why are billable hours used instead of total working hours?
Only invoiced client hours recover operating costs. Total working hours include non-billable activities such as administration, meetings, leave, and business development.
Is hourly overhead the same as a charge-out rate?
No. Hourly overhead is only the operating-cost portion of a rate. A charge-out rate may also include direct delivery costs, profit, and applicable taxes.
How is annual overhead per accountant calculated?
The calculator divides total annual overhead by the number of fee-earning accountants entered. It is an equal-share allocation for planning purposes.
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