How to calculate sale price from margin
Sale price = Cost ÷ (1 − Target margin % ÷ 100)
To hit a 40% margin on a product that costs $40, price = 40 ÷ (1 − 0.40) = 40 ÷ 0.60 = $66.67. You keep $26.67 profit — which is 40% of $66.67, not 40% of cost.
Worked example: from cost to shelf price
Say you source a SKU for $28 and your category needs at least 35% gross margin to cover platform fees and returns:
- Convert margin to decimal: 35% → 0.35
- Divide cost by what's left after margin: $28 ÷ (1 − 0.35) = $28 ÷ 0.65
- Sale price = $43.08 — profit per unit is $15.08
This is the inverse of the profit margin calculator: there you start with price and cost; here you start with cost and the margin you need.
Margin vs markup — why the formula looks backward
A 40% margin is not the same as 40% markup. Markup is profit divided by cost; margin is profit divided by price. At $40 cost, a 40% margin price is $66.67 — that's a 66.7% markup on cost. Telling your team "add 40% on top of cost" prices you at $56 (28.6% margin), not $66.67. Use the markup calculator if you think in markup; use this tool when you know the margin you need for healthy ROAS and break-even targets.
How margin sets your ad budget ceiling
Every margin point changes what you can spend to acquire a sale. At 50% margin your break-even ROAS is 2x; at 40% it's 2.5x; at 25% it's 4x. Price too low and even a respectable campaign ROAS loses money. That's why serious sellers set margin first, then check the target ROAS calculator before scaling spend.
Pricing scenario: promo without destroying margin
You price at $66.67 (40% margin on $40 cost). A 20% off sale drops price to $53.33:
- Profit per unit = $53.33 − $40 = $13.33
- Margin on sale price = 13.33 ÷ 53.33 = 25%
Break-even ROAS jumps from 2.5x to 4x — the promo may need tighter ad targeting or higher AOV bundles to stay profitable. Always run discounts through the discount calculator before launching.
After you set price
Use contribution margin when variable costs beyond COGS apply — shipping, packaging, payment fees. Check break-even units against realistic monthly volume. If margin still looks thin after pricing, revisit cost or promo depth, not just ad creative.
For Amazon and marketplace sellers, remember platform fees count toward variable cost when setting CM — shelf price alone does not tell the full story.