Find the biggest Black Friday discount you can offer without losing money.

Profit per order at each discount

Green = at or above your minimum profit. Amber = thin. Red = you lose money on every order.

Profit = what you keep per order after product cost, shipping, payment fees, expected returns and ad cost. *“Orders needed” = how many times more orders you must sell to earn the same total profit as one full-price order.

profit per order =
    sale price × (1 − returns − fee%)
  − cost × (1 − returns × resale%)
  − shipping − fixed fee
  − returns × return shipping
  − ad cost per order

returns = return rate, fee% = payment fee %, resale% = share of returned items you can resell (all as fractions, e.g. 8% = 0.08).

1. Margin factor m = 1 − return rate − fee %. This is how much of each sale dollar survives refunds and card fees.
2. Fixed costs K = cost × (1 − return rate × resale %) + shipping + fixed fee + return rate × return shipping + ad cost.
3. Break-even price = K ÷ m. Maximum safe price = (K + minimum profit) ÷ m.
4. Discount = 1 − (price ÷ regular price).

Worked example with the defaults: m = 1 − 0.08 − 0.029 = 0.891 and K = $38.63. Break-even price = $38.63 ÷ 0.891 = $43.35 (27.7% off). With a $5 minimum profit the maximum safe price is $48.97 (18.4% off).

Limits: one product at a time; ad cost and return rate are assumed not to change with the discount. Real sales can behave differently, so treat the output as a ceiling to sanity-check, not a forecast.