Discount & Promotion Profit Calculator
Model the true profit impact of percentage discounts, fixed offers, two-for-one, BOGOHP, comps, set menus, vouchers and happy hour. See profit lost per sale, uplift required and best/expected/worst-case scenarios.
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A discount that fills tables can still lose money. This calculator shows the real profit impact of any promotion - percentage off, fixed value, two-for-one, BOGOHP, comps, set menus, vouchers and happy hour.
It compares contribution per order before and after the offer, adds any commission or marketing cost, and works out how much extra volume you need to end up ahead. The scenario planner shows worst, expected and best-case outcomes.
What this calculator does
Models what a discount or offer really costs: the profit given away per sale, and the extra volume you would need to sell just to stand still.
Who it is for
- Operators considering a percentage discount, two-for-one, set menu or happy hour.
- Marketing and ops teams evaluating a voucher or platform promotion.
- Anyone who ran a busy promotion and made less money than the quiet week before.
How to use it
- Enter the normal net selling price and the item or basket cost.
- Choose the promotion type and enter its terms.
- Enter your expected uplift in volume.
- Compare profit per sale before and after, and check the uplift required to break even against your expectation.
The formula
- Normal GP = Net price - Cost
- Promotional GP = Discounted net price - Cost
- Profit lost per sale = Normal GP - Promotional GP
- Break-even uplift% = ((Normal GP / Promotional GP) - 1) x 100
Worked example
A dish at £12.00 net with a £3.60 cost, offered at 25% off.
- Normal GP = £12.00 - £3.60 = £8.40
- Discounted price = £12.00 x 0.75 = £9.00, so promotional GP = £9.00 - £3.60 = £5.40
- Profit lost per sale = £8.40 - £5.40 = £3.00
- Break-even uplift = (£8.40 / £5.40) - 1 = 55.6%
A 25% discount cuts profit per sale by 36% and needs 55.6% more covers just to earn the same money.
How to read your result
- Discounts come entirely out of gross profit, never out of cost, which is why a modest discount does such disproportionate damage.
- The required uplift is almost always larger than people expect, and larger than most promotions deliver.
- Extra volume also brings extra labour, waste and pressure on service, none of which appear in the break-even figure.
What to do next
- Discount into quiet sessions where you have spare capacity, never into a session that already fills.
- Prefer added value - a side, a drink, a fixed price menu - over a straight percentage off, because you give away cost rather than full margin.
- Set the break-even uplift as the success measure before the promotion starts, and check it against actual covers afterwards.
Common mistakes to avoid
- Judging a promotion on revenue or footfall instead of gross profit.
- Discounting your best-selling, best-margin items, where you were never short of demand.
- Forgetting that a two-for-one is effectively a 50% discount on the pair, not a 50% discount on one item.
Assumptions and limitations
- Assumes cost per unit stays constant at higher volume.
- Excludes the labour and capacity cost of extra covers and any long-term effect on what customers expect to pay.
Dumb Bambi provides general business information, not accounting, tax or legal advice. Read our calculation methodology or tell us about a mistake.
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Frequently asked questions
How do I know if a promotion is worth running?+
Compare 'Total promotion profit vs normal' against zero. Positive means it beats normal trading; negative means the discount is deeper than the extra sales can recover.
How much sales uplift do I need?+
The 'Sales uplift required' figure tells you the % more sales needed to match your normal-period profit. If it's above 25–30%, the offer is usually too deep.
Should I include the item cost of a comp item?+
Yes - enter the second item's cost so contribution reflects both items you're serving.
How does this handle voucher and platform commission?+
Enter it as a % of the promotional order. Contribution is calculated after commission, so the profit numbers stay honest.