How to Recalculate Your Margin — and Your Price — After a Cost Increase

A supplier raised a price. Before you decide anything, you need four numbers: what your margin actually is now, what price restores it, what the increase costs you per month, and how much extra volume would be needed if you chose not to reprice. Here's each one, with the arithmetic done out loud.

The setup

We'll use one SKU throughout — a brake pad set that has been a steady seller.

1. Your real margin now

Gross margin is profit as a percentage of the selling price:

margin % = (price − cost) ÷ price × 100

Before: (14 − 6) ÷ 14 = 57.1%. After: (14 − 9) ÷ 14 = 35.7%.

A 50% cost increase took 21 margin points off a product whose price never moved. Note how differently the two percentages behave — the cost went up by half, the margin fell by well over a third. That asymmetry is why cost creep is so much more dangerous than it feels: percentage changes on the cost side land amplified on the margin side.

2. The hold-margin price

The price that restores your target margin at the new cost:

new price = new cost ÷ (1 − target margin)

To get back to 57.1%: 9 ÷ (1 − 0.571) = $20.98. To hit a more modest 45% floor: 9 ÷ 0.55 = $16.36.

The mistake to avoid here is passing the increase through one-for-one: cost rose $3, so add $3 to the price → $17.00. That gives you (17 − 9) ÷ 17 = 47% — better than 35.7%, but still short of where you were, because a flat pass-through ignores that the dollar profit now has to sit on top of a bigger base. If you want the old margin, you need the division; if you only want the old dollars per unit, the addition is exactly right. Decide which you're defending.

3. What the increase costs you per month

Skip this and you'll spend an afternoon on a SKU that sells twice a year.

monthly impact = (new cost − old cost) × units per month

Here: $3.00 × 25 = $75/month, or $900 a year, from one part number. Run the same line for every SKU on the supplier's new price file and sort descending — the top twenty rows will usually account for most of the damage, and the long tail can wait for your next scheduled price review.

4. The volume you'd need if you don't reprice

"We'll just sell more of them" is a legitimate strategy, but it's worth knowing what it commits you to:

required volume ratio = old profit per unit ÷ new profit per unit

Here: $8.00 ÷ $5.00 = 1.6. You'd need to sell 60% more units at the same price to make the same gross profit you made before the increase. Not impossible — but it should be a plan with a mechanism behind it, not a hope.

The mirror version is just as useful when you do raise prices. If you go to $16.36, profit per unit rises from $5.00 to $7.36, so you can afford to lose up to 32% of your units (5.00 ÷ 7.36 = 0.68) before you're worse off than doing nothing. That's usually a much bigger cushion than merchants expect, and it's the number that makes a price increase feel less frightening.

Which SKUs to actually touch

With the four numbers in hand, the decision gets simple. A workable triage:

• Below your margin floor and high volume → reprice now. These are actively costing you money every day you wait.
• Below floor, low volume → batch them into your next quarterly price review, or drop the item if the supplier has priced it out of relevance.
• Still above floor but trending → leave the price, watch the next file. Two consecutive increases on the same line is a supplier pattern, not an event.
• Now selling below cost → fix today, and check whether it's a data error before it's a pricing decision. Unit-of-measure mismatches (a case price landing in a per-unit field) show up here first.

And some things override the arithmetic entirely: a competitor's visible price, a MAP policy from the brand, a psychological price point ($19.99 vs $21.00), or a loss-leader you keep cheap on purpose. The math tells you what a price change is worth — it doesn't tell you what the market will accept. That judgment stays yours.

The five-minute version

1. Get the old and new cost side by side for every affected SKU.
2. Compute the new margin at your current retail — not at whatever retail you had when you last set the price.
3. Flag everything under your floor.
4. Multiply the cost delta by monthly units and sort by dollars.
5. Reprice the top of that list to new cost ÷ (1 − target margin), sanity-check against the market, and move on.