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Methodology

Utilisation to Headcount Planner methodology

Translate billable demand into required delivery headcount.
Duc Nguyen X.By Duc Nguyen X.· Founder, Margin101Last reviewed: View update historyMethodology

Educational only: Business decision support, not accounting, tax or legal advice.

Privacy: Calculations run locally; Margin101 does not receive your commercial inputs.

Update policy: Reviewed when formulas or official dependencies change.

Scope: Market-neutral small-business planning using your own assumptions.

1. Formulas and units

Required Headcount
requiredHeadcount = ceil(required billable hours ÷ billable capacity per person)

Where

requiredBillableHours
Required billable hours (hours/period)Source: User assumption
requiredHeadcount
Required Headcount (count)Source: Calculated output
billableCapacityPerPerson
Billable Capacity Per Person (hours/period)Source: Calculated output
Billable Capacity Per Person
billableCapacityPerPerson = available hours per person × target utilisation

Where

availableHoursPerPerson
Available hours per person (hours/person/period)Source: User assumption
targetUtilisation
Target utilisation (proportion of paid capacity billable)Source: User decision
billableCapacityPerPerson
Billable Capacity Per Person (hours/period)Source: Calculated output
Headcount Gap
headcountGap = required headcount − current headcount

Where

currentHeadcount
Current headcount (people)Source: Business record
requiredHeadcount
Required Headcount (count)Source: Calculated output
headcountGap
Headcount Gap (count)Source: Calculated output
Current Billable Capacity
currentBillableCapacity = current headcount × billable capacity per person

Where

currentHeadcount
Current headcount (people)Source: Business record
billableCapacityPerPerson
Billable Capacity Per Person (hours/period)Source: Calculated output
currentBillableCapacity
Current Billable Capacity (hours/period)Source: Calculated output
Capacity Gap Hours
capacityGapHours = required billable hours − current billable capacity

Where

requiredBillableHours
Required billable hours (hours/period)Source: User assumption
currentBillableCapacity
Current Billable Capacity (hours/period)Source: Calculated output
capacityGapHours
Capacity Gap Hours (hours/period)Source: Calculated output

Money inputs and outputs use the currency selected in the scenario without changing the canonical methodology. Rates, margins, utilisation and buffers are entered as percentages and converted to decimal values for calculation.

2. Worked example

Input assumptions

The worked rows are rendered from the registered engine and visible default fixture.

Required billable hours
1,000 hours/period
Available hours per person
160 hours/person/period
Target utilisation
0.75 proportion of paid capacity billable
Current headcount
7 people

Calculation and outputs

  1. requiredHeadcount

    requiredHeadcount = ceil(required billable hours ÷ billable capacity per person)
    Required billable hours
    1,000 hours/period
    Available hours per person
    160 hours/person/period
    billableCapacityPerPerson
    120 declared output unit
    currentBillableCapacity
    840 declared output unit
    capacityGapHours
    160 declared output unit

    Engine result: 9

  2. billableCapacityPerPerson

    billableCapacityPerPerson = available hours per person × target utilisation
    Required billable hours
    1,000 hours/period
    Available hours per person
    160 hours/person/period
    Target utilisation
    0.75 proportion of paid capacity billable
    capacityGapHours
    160 declared output unit

    Engine result: 120

  3. headcountGap

    headcountGap = required headcount − current headcount
    Required billable hours
    1,000 hours/period
    Current headcount
    7 people
    requiredHeadcount
    9 declared output unit
    currentBillableCapacity
    840 declared output unit

    Engine result: 2

  4. currentBillableCapacity

    currentBillableCapacity = current headcount × billable capacity per person
    Required billable hours
    1,000 hours/period
    Available hours per person
    160 hours/person/period
    Current headcount
    7 people
    requiredHeadcount
    9 declared output unit
    billableCapacityPerPerson
    120 declared output unit
    headcountGap
    2 declared output unit
    capacityGapHours
    160 declared output unit

    Engine result: 840

  5. capacityGapHours

    capacityGapHours = required billable hours − current billable capacity
    Required billable hours
    1,000 hours/period
    Available hours per person
    160 hours/person/period
    Current headcount
    7 people
    requiredHeadcount
    9 declared output unit
    billableCapacityPerPerson
    120 declared output unit
    currentBillableCapacity
    840 declared output unit

    Engine result: 160

Example

The worked rows are rendered from the registered engine and visible default fixture.

Billable Capacity Per Person
120 hours/period
Required Headcount
9
Headcount Gap
2
Current Billable Capacity
840 hours/period
Capacity Gap Hours
160 hours/period

The exact engine-derived outputs are shown in the labelled rows below.

Interpretation

The utilisation to headcount result uses only the entered commercial assumptions.

3. Validation and boundary checks

  • Inputs must be finite and remain within the visible boundaries.
  • Rates are decimal values and all monetary inputs use one consistent currency and period.
  • Whole operational capacity is rounded only where the engine explicitly applies floor or ceiling.
Required billable hours minimum
requiredBillableHours ≥ 0 hours/period — A lower value is rejected before calculation.
Required billable hours maximum
requiredBillableHours ≤ 10,000,000 hours/period — A higher value is rejected before calculation.
Available hours per person minimum
availableHoursPerPerson ≥ 0 hours/person/period — A lower value is rejected before calculation.
Available hours per person maximum
availableHoursPerPerson ≤ 10,000,000 hours/person/period — A higher value is rejected before calculation.
Target utilisation minimum
targetUtilisation ≥ 0 proportion of paid capacity billable — A lower value is rejected before calculation.
Target utilisation maximum
targetUtilisation ≤ 0.99 proportion of paid capacity billable — A higher value is rejected before calculation.
Current headcount minimum
currentHeadcount ≥ 0 people — A lower value is rejected before calculation.
Current headcount maximum
currentHeadcount ≤ 10,000,000 people — A higher value is rejected before calculation.

4. Assumptions and source classification

  • All costs, prices, hours, probabilities and volumes are user-supplied; no market benchmark is inferred.
  • Tax is outside these neutral commercial comparisons.
  • The engine retains full precision; formatting never feeds back into calculation.

This planner has no current policy-data dependency. Its commercial assumptions are user supplied. Registered family-level regression suites exercise the shared business-logic engine and worked-result reconciliation.

5. Limitations

  • The model does not predict demand, delivery performance, contract enforceability or customer behaviour.
  • It does not replace accounting, tax, legal or financial advice.

This is educational decision support, not tax, accounting, legal or financial advice. Check the treatment of your actual transactions under the rules that apply to your business and seek qualified advice where appropriate.

6. Update and evidence policy

Registered family-level suites test formula invariants and example reconciliation; the release ledger records that coverage without claiming a separate oracle for every line of public copy. There is no official threshold or benchmark to refresh for this planner. Commercial inputs remain user-supplied because they vary by business and contract.

Change history

  1. : Initial public release of the planner and methodology after pre-launch calculation, content, source and interaction review.

Related reading

Guides to interpret the decision and its assumptions.

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