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Cost Allocation by Headcount Calculator

Enter the total cost and headcounts to find a department's allocated share.

How it is calculated

The shared cost is divided evenly per person and then multiplied by the department's staff: cost per head = total cost ÷ total headcount, allocation = cost per head × department headcount, share % = department headcount ÷ total headcount × 100. Total headcount is everyone across all departments, including the department you are calculating for. The department headcount cannot be negative or larger than the total, and the total must be above zero; otherwise no result is shown. A department with 0 people gets an allocation of zero. The cost is in dollars, and the headcounts can be employee counts or full-time equivalents, as long as both use the same unit.

Worked example

A company pays 84,000 a year for shared office services. It has 120 employees in total, and the sales department has 18 of them. Cost per head is 84,000 ÷ 120 = $700.00. The sales allocation is 700 × 18 = $12,600.00. Sales holds 18 ÷ 120 × 100 = 15.00% of the headcount, and 15% of 84,000 is the same 12,600. The other departments carry the remaining $71,400.

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Common mistakes

  • Leaving the department out of the total headcount: the total must include it, so 18 of 120 is correct, whereas 18 of 102 would overcharge the department.
  • Mixing full-time and part-time counts: if one department is entered as people and another as full-time equivalents, the shares no longer add up fairly.
  • Using the headcount at a single date for a full year of cost: if staffing changed during the year, use an average headcount for the period.
  • Using headcount for costs that follow something else: costs driven by revenue, machine hours or floor area are not fairly split by number of people.

About this calculator

Shared costs — rent, IT support, a shared HR team's salaries — rarely belong to one department, so businesses need a fair way to split them across cost centers. Allocation by headcount is one of the most common bases: each department's share of the total cost equals its share of total staff, i.e. (department headcount ÷ total headcount) × total cost. It's simple and defensible for costs that genuinely scale with people, like office space or a shared benefits administrator, though it's a poor fit for costs that scale with revenue or usage instead.

This calculator takes the total shared cost and each department's headcount and returns the allocated dollar amount for a chosen department. Finance and accounting teams building internal cost-allocation reports, department managers reviewing their charged-back overhead, and startup founders setting up cost-center budgeting for the first time use it to produce a transparent, headcount-based split that's easy to explain and audit.

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Comments (1)

  • Editorial team

    A quick check across the whole organisation: run each department in turn and add up the allocations. They should equal the total cost, and the percentage shares should reach 100. If they do not, the department headcounts do not add up to the total headcount you entered. Headcount suits costs that follow staff numbers, but floor space or equipment may follow a different driver. Which basis do you use for shared costs besides headcount?

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