Scale a size breakdown to any new quantity
You ordered 45 shirts last time in a size run that worked. Now you need 120, but you want the same ratio of S to M to L to XL. Enter your old breakdown and a new total - we keep the exact ratio, round to whole pieces, and put any leftover units on your biggest sizes so it always adds up. Free, no login, works on any breakdown: sizes, colors, or ship-to locations.
Keep the same ratio, change the total
Reordering at a different quantity but the same size run is one of the most common things a promotional products buyer does - and one of the easiest to get wrong by hand. Straight multiplication leaves you with fractions of a shirt; rounding each size on its own rarely adds up to the total you actually want. This calculator does it properly: it preserves the ratio, rounds to whole pieces, and lands on your new total exactly.
How it works
- Enter your current breakdown. One row per size, color, or ship-to location, with the quantity from last time. Labels are optional.
- Enter the new total quantity. Larger or smaller - the math works both ways.
- We scale by the exact same ratio. Each size is multiplied by new total / old total, then rounded down to a whole piece.
- Leftover pieces go to your largest sizes. Rounding down almost always leaves a few units short of the new total. We hand those out one at a time to your biggest quantities, so the breakdown always adds up to exactly what you asked for.
Worked example: last order was S 10, M 20, L 15 - a total of 45. You want 100 this time. Scaling by 100 / 45 gives S 22.2, M 44.4, L 33.3. Rounded down that is 22 + 44 + 33 = 99, one short. The leftover piece goes to the largest size (M), so the final run is S 22, M 45, L 33 = 100 - same ratio, perfect total.
Why the leftover goes to the largest sizes
When a ratio does not divide evenly into the new total, a handful of pieces have to land somewhere. Putting them on the largest quantities keeps the percentage error the smallest in relative terms, and it matches how buyers actually think - your most-ordered sizes are the safest place to carry an extra unit or two. The calculator flags exactly which rows received a rounding piece so nothing is hidden.
Frequently asked questions
How do I scale an order to a new quantity but keep the same size ratio?
Enter each size and its current quantity, then enter your new total. The calculator multiplies every size by the same factor (new total divided by old total), rounds to whole pieces, and distributes any leftover units to your largest sizes so the result keeps the original ratio and adds up to the new total exactly.
What happens to the remainder when the ratio does not divide evenly?
Rounding each size down usually leaves the order a few pieces short of the new total. Those leftover pieces are added one at a time to the sizes with the highest quantities, so the breakdown always sums to your new total. Rows that received a rounding piece are marked.
Can I use this for colors or ship-to locations instead of sizes?
Yes. The label on each row is free text. Use it for apparel sizes, color counts, decoration locations, or per-store ship quantities - any breakdown where you want to keep the same proportions at a new total.
Does it work when I am ordering fewer pieces than before?
Yes - scaling down works the same way. Note that very small sizes can round to zero when you shrink the total a lot; when that happens the leftover pieces still go to your largest sizes so the total stays correct.
Is the calculation done on my device?
Yes. All the math runs in your browser - nothing is uploaded and no account is needed. You can copy a shareable link that reproduces your exact breakdown for a coworker or customer.
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