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Methodology

Discount Profit Impact Planner methodology

This planner compares gross profit at the current price and volume with a proposed discount and expected volume. It also solves for the units required to preserve baseline gross profit.
Duc Nguyen X.By Duc Nguyen X.Ā· 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

Baseline gross profit
Gā‚€ = (P āˆ’ C) Ɨ Qā‚€

Where

P
current price excluding indirect tax (currency units/unit)Source: Business record
C
unit variable cost excluding indirect tax (currency units/unit)Source: Business record
Qā‚€, Qā‚‘
baseline and expected units (units)Source: User assumption
Gā‚€, Gā‚‘
baseline and scenario gross profit (currency units)Source: Calculated output
Discounted price
Pā‚‘ = P Ɨ (1 āˆ’ d)

Where

P
current price excluding indirect tax (currency units/unit)Source: Business record
d
discount rate (decimal)Source: User decision
Pā‚‘
discounted price (currency units/unit)Source: Calculated output
Scenario gross profit
Gā‚‘ = (Pā‚‘ āˆ’ C) Ɨ Qā‚‘

Where

C
unit variable cost excluding indirect tax (currency units/unit)Source: Business record
Qā‚€, Qā‚‘
baseline and expected units (units)Source: User assumption
Pā‚‘
discounted price (currency units/unit)Source: Calculated output
Gā‚€, Gā‚‘
baseline and scenario gross profit (currency units)Source: Calculated output
Required units
Qįµ£ = Gā‚€ Ć· (Pā‚‘ āˆ’ C)

Where

C
unit variable cost excluding indirect tax (currency units/unit)Source: Business record
Pā‚‘
discounted price (currency units/unit)Source: Calculated output
Gā‚€, Gā‚‘
baseline and scenario gross profit (currency units)Source: Calculated output
Qįµ£
units required to preserve baseline profit (units)Source: Calculated output
Operational whole units
Qw = āŒˆQįµ£āŒ‰

Where

Qįµ£
units required to preserve baseline profit (units)Source: Calculated output
Qw
whole units required to meet or exceed baseline profit (units)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

At a price of 100 currency units excluding indirect tax, a unit cost of 60 currency units and 100 units sold, baseline gross profit is 4,000 currency units.

Calculation and outputs

Example

At a price of 100 currency units excluding indirect tax, a unit cost of 60 currency units and 100 units sold, baseline gross profit is 4,000 currency units.

Baseline gross profit
4,000.00 currency units
Discounted price
90.00 currency units
Scenario gross profit
3,900.00 currency units
Required units
133.33 mathematical units; 134 whole units to meet or exceed baseline profit

A 10% discount leaves 30 currency units gross profit per unit, so 133.34 units are required mathematically; an operator must sell at least 134 whole units to exceed baseline gross profit.

Interpretation

Use the recovery-volume result to judge the commercial burden of a discount, not as a forecast that demand will appear.

3. Validation and boundary checks

  • A zero discount requires the same baseline units to preserve profit.
  • A discounted price at or below unit cost returns a typed non-viable state with null recovery thresholds; success, trace, URL and CSV surfaces never receive Infinity.
  • The engine retains full precision; the UI rounds required whole units upward for the decision display.

4. Assumptions and source classification

  • Price, cost, volume and discount are user-supplied assumptions rather than benchmarks.
  • All commercial amounts are ex indirect tax so indirect tax collected does not inflate gross profit.
  • Unit cost is constant across the tested volume range.

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 excludes fixed-cost changes, capacity constraints, refunds, channel fees, tax and demand elasticity.
  • It does not predict customer response or recommend a discount depth.

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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