Fixed Price vs Hourly Planner methodology

contributionDifference = fixed-price contribution − hourly contribution

protectedFixedRevenue = fixed fee × (1 + scope buffer)

breakEvenHours = protected fixed revenue ÷ hourly rate

expectedFixedContribution = Σ(fixed case contribution × probability)

expectedHourlyContribution = Σ(hourly case contribution × probability)

bestFixedContribution = protected fixed revenue − best hours × delivery cost

bestHourlyContribution = best hours × (hourly rate − delivery cost)

baseFixedContribution = protected fixed revenue − base hours × delivery cost

baseHourlyContribution = base hours × (hourly rate − delivery cost)

worstFixedContribution = protected fixed revenue − worst hours × delivery cost

worstHourlyContribution = worst hours × (hourly rate − delivery cost)

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.

• 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.
• The fixed-fee buffer marks up entered fixed revenue by multiplying the fee by one plus the buffer rate; it does not alter delivery cost.

Hourly billing rate minimum

hourlyRate ≥ 0 currency units/hour — A lower value is rejected before calculation.

Hourly billing rate maximum

hourlyRate ≤ 10,000,000 currency units/hour — A higher value is rejected before calculation.

Fixed project fee minimum

fixedFee ≥ 0 currency units/project — A lower value is rejected before calculation.

Fixed project fee maximum

fixedFee ≤ 10,000,000 currency units/project — A higher value is rejected before calculation.

Delivery cost per hour minimum

deliveryCostPerHour ≥ 0 currency units/hour — A lower value is rejected before calculation.

Delivery cost per hour maximum

deliveryCostPerHour ≤ 10,000,000 currency units/hour — A higher value is rejected before calculation.

Fixed-fee scope buffer minimum

scopeBufferRate ≥ 0 proportion of delivery cost added as scope buffer — A lower value is rejected before calculation.

Fixed-fee scope buffer maximum

scopeBufferRate ≤ 0.99 proportion of delivery cost added as scope buffer — A higher value is rejected before calculation.

Best-case hours minimum

bestCaseHours ≥ 0 hours/project — A lower value is rejected before calculation.

Best-case hours maximum

bestCaseHours ≤ 10,000,000 hours/project — A higher value is rejected before calculation.

Best-case probability minimum

bestCaseProbability ≥ 0 decimal probability — A lower value is rejected before calculation.

Best-case probability maximum

bestCaseProbability ≤ 0.99 decimal probability — A higher value is rejected before calculation.

Base-case hours minimum

baseCaseHours ≥ 0 hours/project — A lower value is rejected before calculation.

Base-case hours maximum

baseCaseHours ≤ 10,000,000 hours/project — A higher value is rejected before calculation.

Base-case probability minimum

baseCaseProbability ≥ 0 decimal probability — A lower value is rejected before calculation.

Base-case probability maximum

baseCaseProbability ≤ 0.99 decimal probability — A higher value is rejected before calculation.

Worst-case hours minimum

worstCaseHours ≥ 0 hours/project — A lower value is rejected before calculation.

Worst-case hours maximum

worstCaseHours ≤ 10,000,000 hours/project — A higher value is rejected before calculation.

Worst-case probability minimum

worstCaseProbability ≥ 0 decimal probability — A lower value is rejected before calculation.

Worst-case probability maximum

worstCaseProbability ≤ 0.99 decimal probability — A higher value is rejected before calculation.

• 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.

• 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.

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.

1. 2026-07-31: Initial public release of the planner and methodology after pre-launch calculation, content, source and interaction review.