# Headcount Planning Calculator

> Work out how many people to hire to reach a target headcount when some staff will leave: growth hires plus replacements for expected attrition.

Category: Salary, HR & payroll · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/hr-headcount-plan-calculator

Reaching a target headcount takes more hires than the gap suggests, because some people will leave along the way. This calculator adds expected replacements to the growth you plan.

Also called: Hiring plan calculator, Workforce planning calculator.

## Inputs
- Current headcount (unit employees; default 100)
- Target headcount at end of period (unit employees; default 120)
- Expected annual attrition (unit % a year; default 15)
- Planning period (unit months; default 12)

## Results
- Total hires needed
- Net headcount change
- Replacement hires for leavers
- Hires per month

## Formula

```
Expected leavers = ⌈(Current + Target) ÷ 2 × Attrition% × Months ÷ 12⌉;  Total hires = max(0, Target − Current + Expected leavers)
```

Where:
- ⌈ ⌉: rounded up to whole people
- Attrition%: annual rate, scaled to the planning period

## Worked example
1. Average headcount = (100 + 120) ÷ 2 = 110.
2. Expected leavers = 110 × 15% = 16.5, rounded up to 17.
3. Total hires = 20 growth + 17 replacements = 37, about 3.08 a month.

**Result:** Growing from 100 to 120 people with 15% attrition takes about 37 hires over the year.

## What the result means

Use the monthly figure to size your recruiting capacity. Hires take time to start, so begin recruiting earlier than the month you need the person.

## Assumptions and limits
- Attrition applies to the average headcount over the period and runs at a steady annual rate.
- Every leaver is replaced.
- Notice periods, time to fill and offer declines are not modelled; add a buffer if your pipeline is slow.

## Questions

### Why use average headcount for leavers?

As the team grows, there are more people who could leave. Averaging start and target reflects that for steady growth.

### What if I am reducing headcount?

Enter a lower target. If expected attrition covers the reduction, the hires needed fall to zero.

## Related calculators
- [Employee Attrition Rate Calculator](https://calculators.geekmidst.com/calculators/employee-attrition-rate-calculator)
- [Employee Retention Rate Calculator](https://calculators.geekmidst.com/calculators/employee-retention-rate-calculator)
- [Time to Hire Calculator](https://calculators.geekmidst.com/calculators/time-to-hire-calculator)
- [Cost per Hire Calculator](https://calculators.geekmidst.com/calculators/recruitment-cost-per-hire-calculator)

Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/hr-headcount-plan-calculator