Make vs Buy Comparison methodology

leftIncrementalCost = make incremental fixed cost + required units × make incremental cost per unit, if capacity is sufficient

rightIncrementalCost = buy incremental fixed cost + required units × buy incremental cost per unit, if capacity is sufficient

crossoverUnits = ceiling((right fixed cost − left fixed cost) / (left unit cost − right unit cost)), when reachable within both capacities

leftCapacityGap = max(0, required units − make capacity)

rightCapacityGap = max(0, required units − buy capacity)

excludedSunkCost = current sunk cost disclosed but excluded from both incremental options

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.

• All inputs must be finite and remain inside the visible non-negative validation boundaries.
• Capacity and demand fields that represent physical units reject fractional values where the engine requires whole units.
• Rates remain inside the closed range from 0% to 100%.
• Unreachable contribution, crossover or payback thresholds return an explicit unavailable state rather than Infinity.
• Option comparisons reject an infeasible option when its entered capacity is below the required workload.

Required units minimum

units ≥ 0 units/period — A lower value is rejected before calculation.

Required units maximum

units ≤ 100,000,000 units/period — A higher value is rejected before calculation.

Current sunk cost minimum

currentSunkCost ≥ 0 currency units/decision period, ex tax — A lower value is rejected before calculation.

Current sunk cost maximum

currentSunkCost ≤ 10,000,000 currency units/decision period, ex tax — A higher value is rejected before calculation.

Make incremental fixed cost minimum

leftIncrementalFixedCost ≥ 0 currency units/decision period, ex tax — A lower value is rejected before calculation.

Make incremental fixed cost maximum

leftIncrementalFixedCost ≤ 10,000,000 currency units/decision period, ex tax — A higher value is rejected before calculation.

Make incremental cost per unit minimum

leftIncrementalVariableCostPerUnit ≥ 0 currency units/unit, ex tax — A lower value is rejected before calculation.

Make incremental cost per unit maximum

leftIncrementalVariableCostPerUnit ≤ 10,000,000 currency units/unit, ex tax — A higher value is rejected before calculation.

Make capacity minimum

leftCapacityUnits ≥ 0 units/period — A lower value is rejected before calculation.

Make capacity maximum

leftCapacityUnits ≤ 100,000,000 units/period — A higher value is rejected before calculation.

Buy incremental fixed cost minimum

rightIncrementalFixedCost ≥ 0 currency units/decision period, ex tax — A lower value is rejected before calculation.

Buy incremental fixed cost maximum

rightIncrementalFixedCost ≤ 10,000,000 currency units/decision period, ex tax — A higher value is rejected before calculation.

Buy incremental cost per unit minimum

rightIncrementalVariableCostPerUnit ≥ 0 currency units/unit, ex tax — A lower value is rejected before calculation.

Buy incremental cost per unit maximum

rightIncrementalVariableCostPerUnit ≤ 10,000,000 currency units/unit, ex tax — A higher value is rejected before calculation.

Buy capacity minimum

rightCapacityUnits ≥ 0 units/period — A lower value is rejected before calculation.

Buy capacity maximum

rightCapacityUnits ≤ 100,000,000 units/period — A higher value is rejected before calculation.

• All operating volumes, rates, workload, capacity, time, cost and contribution values are supplied by the user.
• Money inputs use one consistent ex-tax basis and every record refers to the same operating period.
• Demand realisation, recovery, hours saved and expected unit rates are scenarios, not forecasts or benchmarks.
• Committed sunk cost is disclosed but excluded from make, buy, outsource and hire incremental economics.
• The shared engine retains raw precision and display formatting never feeds back into calculation.

This comparison calculator 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.

• Results depend on complete and comparable incremental cost, capacity and operating records.
• The model does not forecast demand, service quality, employee performance, supplier reliability or disruption duration.
• A positive result or short payback does not establish implementation feasibility or guarantee a commercial outcome.
• The planner does not replace operational, 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 comparison calculator. 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.