Markup and margin both describe the gap between what a product costs you and what you sell it for, which is exactly why they get mixed up. But they're calculated differently, and confusing them is a sneaky way to underprice yourself. A few minutes here saves you from a common, costly mistake.
Markup is based on your cost
Markup is how much you add on top of your cost, as a percentage of the cost. If a product costs you $10 and you mark it up 50%, you add $5 and sell at $15. Markup is the lens you use when setting a price from a true cost.
Margin is based on your price
Margin is how much profit you keep, as a percentage of the selling price. That same $15 product with $10 cost has $5 of profit, but as a share of the $15 price, that's a 33% margin, not 50%. Same dollars, different percentage.
A 50% markup is only a 33% margin. Mix them up and you'll think you're making more than you are.
Why the mix-up costs you
If you mean to keep a 50% margin but accidentally apply a 50% markup, you'll price too low and keep less than you planned. The bigger the number, the bigger the gap: a 100% markup is only a 50% margin. When you set targets, be clear which one you mean.
Let the tool do the math
The safest fix is to not do this in your head. Keepsel works from your true cost and shows the price and margin together, so you can price to a real margin target without accidentally turning a markup into a smaller margin than you intended. The free pricing calculator shows both too.