Here’s the truth that stings a little: “10% off” feels harmless, but it often vaporizes profit unless volume skyrockets. Before you run a promo, sanity, check the math. The breakeven lift is usually much higher than teams expect, and the long tail of lower reference prices can haunt future margins. Use the quick snapshots below to frame the decision, then we’ll move into the calculator.
10% Off: Quick Reality Check
- 20% margin → need +100% units
- 30% margin → need +50% units
- 40% margin → need +33% units
- Very high margins and excess capacity
- Clearance for end-of-life items with low cannibalization
- New-customer acquisition where LTV covers the hit
- Price-fenced offers for specific segments only
- Lower reference price that lingers
- Promo shoppers who rarely return
- Coupon stacking and affiliate bleed
- Higher support and return rates erase gains
| Baseline Margin | Units Needed |
|---|---|
| 15% | +200% |
| 20% | +100% |
| 25% | +67% |
| 30% | +50% |
| 35% | +40% |
| 40% | +33% |
- Bundle add-ons instead of price cuts
- Free expedited shipping on high-margin SKUs
- Tiered perks for spend thresholds
- Targeted loyalty credits that expire
- Forecasted lift ≥ required lift above
- LTV uplift or CAC offset documented
- Price fence defined by segment or channel
- Post-promo price reset plan in place
Discounting Profit Trap
Shows how much extra volume you need to break even after a discount and the profit impact.
Results
Show math
Baseline orders = Q₀ = T·c. Profit per order = m·P. Baseline profit = Q₀·m·P.
After discount, profit per order = (m − d)·P.
Break-even requires Q₁(m − d)·P = Q₀·m·P ⇒ Q₁/Q₀ = m/(m − d).
Break-even lift = (Q₁/Q₀ − 1) = d/(m − d).
Profit change if conversion does not change: Δ = Q₀[(m − d) − m]·P = −Q₀·d·P. Percent change = −d/m.
We built this calculator because we’ve seen too many businesses throw out discounts without running the numbers. Sometimes it works. Sometimes it wrecks your margins. This gives you a clear, fast way to pressure-test your assumptions before you roll out a promotion. Hope it helps you make smarter, more profitable decisions.
