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A 10% discount at 30% margin needs +50% volume just to break even. Discounts come 100% out of margin, never out of costs — revenue grows while profit dies.
The most dangerous sentence in small business is "we will make it up on volume." The arithmetic: at a 30% gross margin, a 10% price cut requires FIFTY percent more volume to produce the same profit — because discounts come entirely out of margin, not out of costs. At 20% margin the same cut needs double the volume. Sales teams celebrate the revenue line while the profit line dies quietly. This calculator prices any discount against your real margin and your actual volume expectation — including the cases where discounting genuinely wins: idle capacity, expiring inventory, and contracted volume.
Business owners use it before quoting a discount: a 10% cut at 30% margin needs +50% volume to break even — discounts come 100% out of margin, and "make it up on volume" is the most expensive sentence in small business.
Because of where the discount lands. Revenue is not profit: on a $100 sale at 30% margin, $70 is costs and $30 is profit. A 10% discount takes $10 off the price — but the $70 of costs does not change, so the $10 comes entirely out of the $30: profit per unit drops a third. To hold total profit, you must sell half again as many units. The formula is margin ÷ (margin − discount): at 30% margin and 10% off, 30/20 = 1.5×. The asymmetry gets brutal at thin margins — a 10% cut at 15% margin needs 3× volume, and a discount equal to your margin means infinite volume: you lose money on every sale and make it up on nothing. The same math runs in reverse and is the case for price INCREASES: a 5% price rise at 30% margin can lose 14% of volume and still grow profit. Most small businesses have the lever backwards — terrified of a 5% increase their customers would barely notice, casual about a 10% discount that halves their margin.
When the margin assumption changes — which is specific, not vibes. Idle capacity: the empty hotel room, the unbooked Tuesday crew, the flight seat at the gate — when marginal cost is near zero, ANY price above it adds profit, and the breakeven formula collapses. That is why hotels discount same-day and manufacturers run third shifts cheap. Expiring inventory: perishables, seasonal goods, last-year models — the alternative to the discount is zero, so the margin comparison is against salvage value, not full price. Contracted volume: a customer signing for the +50% in writing converts hope into arithmetic — the discount earns its volume instead of wishing for it. And strategic loss-leaders WITH a measured attachment rate: the discounted item whose buyers reliably buy full-margin items too — measure the attachment honestly, because unmeasured loss-leaders are just losses. What never qualifies: competitive panic matching (the competitor's price may be their mistake, not your mandate), end-of-quarter revenue rescue (customers learn the calendar and wait), and discounting to customers who would have paid full price — the unmeasurable leak that margins die from.
Anything that costs you less than the discount while feeling like value to them — the margin-preserving menu. Add value: priority scheduling, extended warranties, free consumables, training, white-glove delivery — perks that cost 20–40 cents per dollar of perceived value beat a dollar-for-dollar price cut. Unbundle: strip the offer to a cheaper tier (less service, slower delivery, self-serve) — the customer who wanted a lower price gets one, and your full-margin offer stays intact for everyone else; this also flushes out whether they wanted cheap or wanted the deal. Change terms instead of price: faster payment for a small discount (the payment-terms calculator prices 2/10-net-30 at a 36% APR — buyers love it, and it costs you less than a straight cut when cash is cheap), deposits and progress billing, or longer commitments for a lower rate (annual contracts at 10% off with LOCKED volume pass the breakeven test by contract). And the discipline that protects all of it: a written discount authority ladder — salespeople discount what they are allowed to, so make anything past 5% require the arithmetic this calculator does, in writing, before the quote leaves.