TL;DR: Markup is profit ÷ cost. Margin is profit ÷ selling price. Same $20 profit on a $80 cost / $100 price is 25% markup and 20% margin. If you report 25% margin, a buyer who thinks in margin thinks you are richer than you are. Denominator is the whole personality of the percent.
Dollars first, percents second
Cost $80, sell $100, profit $20. Those three dollars must exist before either percent. If you only have a 25% markup target and a cost, selling price = cost × 1.25. If you only have a 20% margin target and a cost, selling price = cost / (1 − 0.20) = cost / 0.80. That second one is reverse percent, not “multiply by 1.20.” 1.20 would be a 20% markup, a different policy.
People who want 20% margin and multiply cost by 1.20 underprice. $80 × 1.20 = $96, profit $16, margin 16/96 ≈ 16.7%, not 20%. The business felt 20% and the math said 16.7%. Feelings are not denominators.
Why shops talk past each other
Vendors quote markup. Retail buyers quote margin. A “we need 30%” meeting without the word margin or markup is a future invoice dispute. Write the word. Then compute. Percent-of-a-number on profit versus each base gives both percents in two passes: 20/80 and 20/100.
If profit is 0, both percents are 0. If you sell below cost, both are negative. Negative margin is a fire. Negative markup is the same fire with a different volunteer department. Do not hide negatives by taking absolute value to “present better.”
Discounts after markup
Marked 25% above cost, then 10% off the ticket: ticket $100, sale $90, cost $80, profit $10. Markup on the sale path is no longer 25% of cost in realized terms; realized markup = 10/80 = 12.5%. Realized margin = 10/90 ≈ 11.1%. Planned percents are not realized percents. Coupons live in the realized column.
Employee 40% off a $100 ticket that was 25% above $80: 40% of 100 = $40 off, sale $60, which is below $80 cost. The 25% markup did not survive a 40% off ticket. Ticket percents are of ticket, not of cost. Two bases again.
Volume and “average margin”
Item A 20% margin on $1,000 sales, item B 50% margin on $10 sales. Unweighted average of 20 and 50 is 35%. Sales-weighted margin is (200+5)/1010 ≈ 20.3%. Average of percents without weights is a meeting decoration. Weight by the denominator that defines margin (sales), or go back to total profit / total sales.
If costs are missing, you cannot produce markup. Margin needs selling prices and costs too, actually—profit needs both. A sales-only spreadsheet cannot invent 20% margin. It can invent a target. Targets are not measurements.
Tax, shipping, and which cost
Is cost landed (with freight) or factory? Markup on factory looks larger. Honest ops use landed cost as markup’s whole. Margin’s whole is still net selling price after discounts, usually, not list. Define list vs net. A 20% margin on list with 15% off invoices is not 20% in cash.
Sales tax collected is not profit. If you treat tax-inclusive revenue as the margin denominator, you dilute margin. Exclude tax from sales if tax is pass-through. Include it if your books include it everywhere—then include the remittance as cost-like. Consistency beats a clever percent.
Translation table you can memorize
Margin = markup / (1 + markup). Markup = margin / (1 − margin). 25% markup ↔ 20% margin. 100% markup ↔ 50% margin. 0% both. These identities assume the same profit dollars and the two bases cost vs price. If discounts change the price, recompute from dollars. Do not identity-transform a stale 25% from last quarter’s list.
Retail “keystone” and 100% markup
Keystone often means 100% markup: sell at double cost, which is 50% margin. People hear 100% and think 100% margin, which would be selling at infinite price or selling with cost 0. 100% of cost as profit is double; 100% of price as profit is free goods. The same “100%” token is two lives. Say markup or margin every time you say 100% in a pricing meeting.
If a buyer demands 40% margin and a seller thinks in 40% markup, the seller’s price is too low for the buyer’s need: 40% markup is about 28.6% margin. The meeting will feel like bad faith. It is two wholes. Write both percents on the quote. Then the dollars can match.
Freight as cost, not as a mood
If freight is $8 on an $80 factory cost, landed $88, sell $100, profit $12. Markup 12/88 ≈ 13.6%, margin 12/100 = 12%. Using $80 as markup’s whole after you paid $8 freight inflates markup to 25% and lies to you about restocking. Landed cost is the adult whole for markup. If freight is billed to the customer as a line, it may not sit in cost; then it should not sit in the selling-price whole either if it is pass-through. Follow the cash.
Coffee beans versus the cup on the board
A shop pays $4.50 for the beans, milk, and cup that become one latte, and sells it for $6.00. Profit is $1.50. Markup is 1.50/4.50 = 33.3% of cost. Margin is 1.50/6.00 = 25% of the selling price. The owner who tells a lender “we run a thirty-three percent margin” has swapped the denominator and overstated the share of each dollar that is profit. To hit a true 25% margin when the cup costs $4.50, price = 4.50 / 0.75 = $6.00. Multiplying cost by 1.25 yields $5.63, which is a 25% markup and only a 20% margin. The menu board cannot satisfy both sentences with one sticker.
If the milk invoice jumps and the cup cost becomes $5.10 while the board stays $6.00, profit falls to $0.90. Margin is now 0.90/6.00 = 15%. Markup is 0.90/5.10, about 17.6%. Recalculate from the new dollars. Do not subtract “eight percent of something” in your head and hope the sticker still means what it meant in March.
A painter’s materials versus the job price
Materials for a hallway are $240. The painter wants a 40% markup on materials and also says the job should show a 40% margin. Those wishes disagree. Markup price is 240 times 1.40 = $336, profit $96, margin 96/336, about 28.6%. A 40% margin on the same materials means price = 240 / 0.60 = $400, profit $160, markup 160/240, about 66.7%. Quoting $336 while promising a forty percent margin is how a Saturday job turns into a dispute on the invoice. Pick the sentence the estimate actually used, and write the denominator on the estimate so the client is not left to guess which percent they bought.
