Discount Impact Calculator

A discount comes out of margin, not out of price

The reason discounts feel cheaper than they are is that operators judge them against the menu price. Twenty percent off a $42 check sounds like giving away a fifth of something. In reality you are giving away a fifth of the price but a much larger share of the only part of that price you ever get to keep.

Take a $42 check at a 70% gross margin. Your food and beverage cost is $12.60 and your contribution is $29.40. Apply a 20% discount and the guest now pays $33.60. Your cost has not moved — the plate contains exactly the same ingredients — so contribution falls to $21.00. The price dropped by 20%, but the money that pays your rent, payroll and everything else dropped by 28.6%.

That is the whole problem in one line. The discount is subtracted from your margin percentage, not scaled by it. A 25% discount against a 30% margin leaves you five points of contribution on a full-price cost base. A 25% discount against a 75% margin leaves you fifty. Two businesses running the same headline offer can be in completely different positions, which is why copying a competitor's promotion is such a common way to lose money.

How much extra volume the discount has to buy

If contribution per cover falls, the only way to end up where you started is to serve more covers. The number you need is fixed by arithmetic, not by optimism:

Back to the $42 check. Contribution went from $29.40 to $21.00, a ratio of 1.4. You need 40% more covers to generate the same total contribution. If the promotion window normally does 400 covers, you need 560 — 160 extra covers — before the discount has earned you anything at all. Most operators, asked to guess before they calculate, say something close to 20%.

Discount offered	At 65% margin	At 70% margin	At 75% margin
10% off	+18% covers	+17% covers	+15% covers
15% off	+30% covers	+27% covers	+25% covers
20% off	+44% covers	+40% covers	+36% covers
25% off	+63% covers	+56% covers	+50% covers
50% off	+333% covers	+250% covers	+200% covers

The bottom row is worth reading twice. A two-for-one deal, or half price on a set menu, needs you to serve three and a half times your normal volume at a 70% margin just to hold contribution flat. Very few dining rooms have that much physical capacity, and the ones that do rarely have the kitchen and floor staffing to deliver it at quality. If you want to see what your room can actually absorb, work through your table turnover rate first — the ceiling is usually lower than the offer assumes.

Note also that the uplift is measured in covers, not in revenue. A discount that brings in 40% more covers produces only about 12% more revenue at 20% off, because each of those covers pays less. Anyone reporting the promotion as a sales increase is measuring the wrong thing.

Cannibalisation: the covers you were getting anyway

The break-even uplift above assumes the discount applies to everyone. In practice the more useful question is how much margin you hand to guests who would have walked through the door regardless. That group produces no incremental sale at all; they simply pay you less for the same meal.

This is why a targeted offer beats a blanket one even when the discount is deeper. A 30% offer sent only to lapsed guests who have not visited in six months cannibalises almost nothing, because by definition those covers were not coming. The same 30% printed on a table talker is redeemed overwhelmingly by regulars who were already booked.

It also explains the classic Saturday night failure. A discount running at your busiest service has near-total cannibalisation and no capacity for incremental covers, so it converts full-price demand into discounted demand with no upside whatsoever. The room looks identical and the deposit is smaller.

Set the redemption field to your honest estimate of how many of your normal covers will use the offer. If you have no data, 80% is a fair starting point for anything advertised in-house and 30–50% for something distributed to a defined external list.

Why the extra covers usually do not arrive

Even when the break-even uplift looks achievable on paper, three things tend to erode it.

• Discount guests spend less on the rest of the check. Someone attracted by price is less likely to add a second bottle or a dessert, so your average check falls by more than the discount alone. Check your average check during the promotion, not just cover count.
• Variable costs are not perfectly variable. Serving 40% more covers usually means extra hours on the floor and in the kitchen, so the real break-even is above the figure this calculator shows. Contribution margin is the right starting point, but labour steps up in blocks.
• Capacity caps the upside. If your break-even needs 560 covers and the room seats enough for 480 in that window, the promotion cannot succeed no matter how well it is marketed.
• Service quality drops under volume. The covers you gain at a discount are the least forgiving of a slow kitchen, and a bad first visit at a discounted price is worse than no visit.
• Guests learn the pattern. A discount that runs every third Tuesday trains your regulars to stop coming on the other Tuesdays.

Together these mean the observed uplift needed is usually higher than the arithmetic minimum. Treat the calculator's number as the floor, not the target.

When discounting is the right decision

None of this means discounting is always wrong. It means a discount has to do a job that justifies the margin it consumes, and that job has to be something other than filling seats you would have filled anyway.

• Genuinely idle capacity. A Tuesday lunch at 25% occupancy has cannibalisation near zero and fixed costs already sunk. Any positive contribution is better than an empty chair.
• Acquiring a guest you can keep. A discount is defensible if the second visit is at full price. That makes retention the metric, not redemption count.
• Clearing perishable stock. A discounted special built around an ingredient that would otherwise be binned is not really a discount, it is a recovery. Compare it against your food cost on the dish rather than the standard menu margin.
• Shifting demand rather than creating it. An early-evening price that pulls guests out of your 8pm crush can raise total covers without raising capacity.
• Adding value instead of cutting price. A complimentary item with a low cost and a high perceived value costs you its food cost, not a percentage of the whole check. That is almost always the cheaper way to make an offer feel generous.

The last point is the single most useful substitution available. A $4 cost item given away against a $42 check costs 9.5% of the check in margin terms. A 20% discount costs 20%. Guests routinely rate the free item as the better offer.

Before you sign off a promotion

Run the numbers first and write down the answer, because after the fact everyone remembers the room being busy. Four things to fix in advance:

• The break-even cover count, from this calculator, stated as an absolute number for the promotion window.
• The capacity ceiling for that window, so you know whether the break-even is even physically possible.
• The baseline — the same window in a comparable recent period, so you can measure the uplift rather than the total.
• The end date, decided before it starts. Discounts that are extended because they were popular are being extended on the wrong measure.

If you are testing whether the operation can absorb the cost at all, pair this with your break-even calculator and your gross profit margin, and check the discount is not quietly pushing your prime cost past the point where the extra volume stops helping. A promotion that hits its cover target and still loses money is almost always one where the margin was too thin before the discount was applied.

Frequently asked questions

What margin figure should I enter?

Use gross margin on the check — the share left after food and beverage cost. If your combined cost of goods runs 30%, enter 70. Do not use net margin; the calculator is measuring contribution, and your fixed costs do not change because a guest used a voucher.

Why does a 20% discount need 40% more covers?

Because the discount comes out of contribution, not out of price. At a 70% margin a $42 check contributes $29.40. After 20% off it contributes $21.00, since the food cost is unchanged. Restoring $29.40 of contribution from $21.00 covers takes 40% more of them.

Should labour be included in the margin?

Not in the field above, but be aware of it. The calculator uses gross margin, which treats labour as fixed for the period. If the extra covers require additional hours, your true break-even is higher — a reason to treat the result as a minimum rather than a target.

How do I model a two-for-one or a free-starter offer?

Convert it to an effective discount on the whole check. Two-for-one on mains at a site where mains are 60% of the check is roughly a 30% discount overall. A free starter costing $6 against a $42 check is about 14%. The blended figure is what matters, not the headline.

What redemption percentage should I assume?

For an offer promoted in-house or to your existing list, assume most of your regular covers will use it — 80% is a reasonable planning figure. For an offer sent only to lapsed guests or a defined external audience, 30–50% is more typical. Higher redemption means more cannibalisation and a larger cover target.

Do third-party voucher and deal platforms change the calculation?

They make it worse. The platform commission is deducted on top of the discount, so a 25% offer with a 20% commission behaves like a 40% discount on your margin. Enter the combined figure or the result will flatter the promotion substantially.

What if discount guests spend more overall?

Some do, and it is worth measuring rather than assuming. If your discount consistently lifts the pre-discount check — a set menu that adds a drinks spend, for example — enter the higher check and the effective discount against it. In most operations the effect runs the other way.