Price increase percentage calculator
Type the price you paid before and the price on the new list. The percentage is always measured against the old price. Add the units you buy in a year to see what the change is worth in money.
Work backwards from a stated increase
A supplier letter says "prices rise 6%". Check what a line should cost after it, or what it cost before.
The formula
Percentage change = (new price - old price) / old price x 100. In Excel or Google Sheets, with the old price in B2 and the new price in C2, format the cell as a percentage and use:
=C2/B2-1Money per year at your volume, with annual units in D2:
=(C2-B2)*D2Worked example: four lines from one supplier
| Item | Old | New | Change | Units/yr | Per year |
|---|---|---|---|---|---|
| Copper elbow 1/2in | $4.20 | $4.45 | +6.0% | 2,400 | +$600.00 |
| PVC conduit 10ft | $8.95 | $9.75 | +8.9% | 600 | +$480.00 |
| Ball valve 1in | $21.40 | $19.90 | -7.0% | 150 | -$225.00 |
| 12 AWG THHN, 500ft | $84.10 | $91.60 | +8.9% | 40 | +$300.00 |
Net effect across these four lines: +$1,155.00 a year. The biggest cost per year comes from the copper elbow 1/2in at +6.0%, not from the largest percentage (PVC conduit 10ft, +8.9%). Rank by money per year, not by percentage, when you decide what to push back on.
Why an increase and a decrease of the same percentage do not cancel
The base moves. A $100.00 item that rises 10% costs $110.00; a 10% cut from there gives $99.00, not $100.00. To undo an increase of p%, the price has to fall by p / (100 + p) x 100: for 10%, that is 9.09%.
Percent versus percentage points
A margin that drops from 30% to 27% has fallen 3 percentage points, which is a 10% fall in the margin itself. Say which one you mean when you report it upward. The margin impact calculator shows both.
Pricecheck takes the supplier's email as it arrives, PDF included, compares it with the last version and sends back only the lines that moved. $49/mo, first month free for early signups. No payment now.