Work backwards from a target selling price
With a cost of 80 and a selling price of 100, gross profit is 20. Dividing by cost gives 25% markup, while dividing by selling price gives 20% margin. If you instead need a 25% margin, solve price = 80 / (1 - 0.25), giving about 106.67. Adding 25% to cost would produce 100 and miss that margin target.
Keep the cost basis consistent between scenarios. A calculation using purchase cost alone cannot be compared directly with one that includes delivery, packaging and other costs. After a proposed discount, recompute from the discounted selling price: reducing 100 to 90 while cost remains 80 leaves 10 profit and about 11.11% margin. These relationships explain the numbers; they do not determine an appropriate price for a market. Record your assumptions and rounding so another person can reproduce the comparison.
Markup starts from cost
Markup is the percentage added on top of what something costs you. If an item costs 20 and you add a 50% markup, the selling price becomes 30.
That sounds like a 50% profit margin, but it is not. The profit is 10, and 10 is one third of the 30 selling price.
Margin starts from selling price
Margin measures profit as a share of the final selling price. A 40% margin means 40% of the revenue remains as gross profit before overheads and other costs.
This is why teams can talk past each other. Suppliers may quote markup, while accountants and owners often care about margin.
Use both before changing prices
A markup calculator is useful when you know your cost and want to add a fixed percentage. A margin calculator is useful when you know the profitability you need and want to work backward.
For real pricing, include payment fees, tax treatment, shipping, discounts, returns, and overhead in the broader decision. The calculator gives the clean math, not a full business model.
Separate one-time costs from per-sale costs before you compare products. For example, a payment fee charged on every order changes the profit from each sale, while a monthly software subscription belongs in a break-even calculation across many sales. Decide whether displayed prices include tax before entering them, and apply the same convention to every scenario.