Scale percentage
Scale percentage calculator
What you are scaling
Accepts 120, 4.75, 1/8 or 3' 7 1/2".
Enter the number only, for example 150.
Derived from the unrounded factor as k² and k³.
Your answer
125%
This is an enlargement: the result is larger than what you started with.
Bar lengths are proportional to the calculated factor. Read the exact figures below.
- Scale factor
- 1.25×
- Resize percentage
- 125%
- Reverse factor
- 0.8×
- Result
- 300 mm
- Equivalent ratio
- 1.25:1
- Difference
- +60 mm
Exact: 5/4
Enter this in a print dialog or slicer
80% to undo it
300 mm
Result : original, as a representative ratio
Original was 240 mm
Consequences of this factor
| Measure | Multiplier | Of original | Change |
|---|---|---|---|
| Length (k) | 1.25× | +25% | |
| Area (k²) | 1.5625× | +56.25% | |
| Volume (k³) | 1.953125× | +95.3125% |
Area and volume figures are geometric consequences of the length factor. They describe a solid, uniformly scaled shape — not hollow parts, infill, wall thickness or material behaviour.
How this was calculated
Inputs
- Starting measurement: 240 mm = 240 mm
- Percentage: 125% (scale to)
Formula
k = percentage ÷ 100
k = 125 → 5/4
k = 1.25× = 125%
Derived effects
- Area (k²): 1.5625×
- Volume (k³): 1.953125×
- Result size: 240 mm × k = 300 mm
Exact calculation state: 5/4 — displayed values are formatted from this fraction, never re-used after rounding.
Calculated by SnapScaleCalc from the values entered. Methodology
“Scale to” and “increase by” are not the same
At 125%, scaling to that percentage gives 300 mm, while increasing by it gives 540 mm. The selected reading is used above.
How this calculation works
Take the example above: 240 mm going to 300 mm. The percentage to scale to is 125% — the new size as a share of the old. The increase is +25% — the part that was added. Both describe the same 60 mm of growth, and they always differ by exactly 100 points.
Every dialog that asks for a percentage — printer, copier, slicer, photocopier zoom, CAD plot scaling — wants the first one. Type 25 where 125 was meant and the object comes out at a quarter of its size; type 125 where “increase by 125%” was written and you are short by an entire original.
Which reading did you mean?
- Scale to 125% → 240 mm becomes 300 mm.
- Increase by 125% → 240 mm becomes 540 mm, because the original is kept and 125% of it added on top.
- Decrease by 125% → impossible; anything over 100% removes more than exists, and the calculator says so rather than returning a negative length.
What the phrase in front of you actually means
Most percentage errors are translation errors from ordinary English. This table resolves the six phrasings that cause them. Read the row that matches the words you were given, then use the factor column — that is the only unambiguous form.
| Phrase | Factor | Final % | Change % | Interpretation |
|---|---|---|---|---|
| “Scale to 150%” | 1.5 | 150% | +50% | Output is 150% of the input. What print dialogs mean. |
| “Make it 1.5×” | 1.5 | 150% | +50% | Identical to “scale to 150%”, written as a multiplier. |
| “Increase by 50%” | 1.5 | 150% | +50% | Keep the original, add half of it. Same result, other words. |
| “Increase by 150%” | 2.5 | 250% | +150% | Keep the original and add 150% of it. Not 150% — 250%. |
| “Reduce by 30%” | 0.7 | 70% | −30% | Remove 30% of the original; 70% remains. |
| “Scale to 70%” | 0.7 | 70% | −30% | Same operation as “reduce by 30%”. |
The critical pair is rows one and four. Scale to 150% = factor 1.5 = +50%. Increase by 150% = factor 2.5 = final 250%. The same three digits, and a 67% difference in the finished object. Anywhere the two readings would disagree, this calculator shows both results side by side rather than choosing for you — the reading is a control you set, not a guess the page makes.
A percentage cannot be undone by subtracting it
Reduce by 20% and you are at 80%; add 20% back and you are at 96%, not 100%. The correction is the reciprocal — 100 ÷ 0.8 = 125% — which is the same figure the example above produces, for the same reason. Percentages applied one after another multiply, so several of them belong on the scale chain calculator, and a percentage already applied wrongly by a printer belongs on the print scale correction calculator.
What this does not tell you
The percentage is exact arithmetic on the numbers you enter. It does not know whether the device applying it is accurate: printers, copiers and slicers can add their own fit-to-page or shrinkage behaviour, so measure the output before you rely on it.
Area and volume percentages shown here are geometric. Material, weight and cost do not follow them for hollow parts, and structural behaviour does not follow them at all.
Questions people ask about this
- Does “scale to 150%” mean the same as “increase by 150%”?
- No. Scaling to 150% multiplies by 1.5. Increasing by 150% multiplies by 2.5, because you keep the original and add 150% of it on top. This calculator makes you choose which one you mean.
- What percentage halves something?
- 50%, a factor of 0.5. To go back to the original size afterwards you need 200%, not 150% — reversing a percentage is a reciprocal, not a subtraction.
- Why does 80% then 120% not return me to 100%?
- 0.8 × 1.2 = 0.96, so you end up at 96% of the original. Percentages compound by multiplication; the correct correction for 80% is 125%.
- Which percentage do print dialogs use?
- Print dialogs, copiers and slicers all use the “scale to” reading: 75% means each length becomes three quarters of the original.