A 4.5 m car at 1:24
Real to model divides the real size by the scale number: 4500 mm ÷ 24.
187.5 mmScale Calculator for Models, Minis and 3D Prints
Convert real sizes to any model scale and back, work out the ratio between two sizes, and get the exact percentage to type into Bambu Studio, PrusaSlicer or Cura.
Length or height of the real thing
1:72, 72, HO or 28mm
Common scalesTap one to use it
Model size
187.5 mm
7.38 in
4.5 m ÷ 24 = 187.5 mm
At 1:24, real parts thinner than 9.6 mm print thinner than one 0.4 mm line. A 0.2 mm nozzle halves that to 4.8 mm, and resin goes finer still.
Check a model fileDrop an STL, 3MF or OBJ to read its size
Calculated in your browser. Files never leave your device.
Measure, resize or make a model
The calculator gives you the number. These tools read and change the file.
How to use the scale calculator
- 1
Pick what you know
A real size and a scale, a printed size, two sizes to compare, or a model you want at another scale.
- 2
Set the scale
Type a ratio like 1:35, a railway scale like HO, or a figure scale like 28mm. Or tap one of the common scales.
- 3
Copy the result
Read the size in mm or inches, or copy the slicer percentage and paste it into the scale field.
The math, worked out
Four common jobs and the numbers this calculator gives for them.
A 1:35 kit printed at 1:72
Rescale divides the old scale number by the new one: 35 ÷ 72 × 100 is the slicer percentage.
48.61%A 28 mm miniature at 32 mm
Figure scales are heights, so the percentage is 32 ÷ 28 × 100.
114.29%What ratio is 28 mm?
Figure height turns a figure scale into a ratio, here for a 1.8 m adult measured to the eyes.
1:60.1Why use this model scale calculator
One scale tool for kits, trains, miniatures and any 3D print you want at another size.
Five calculators in one
Real to model, model to real, find the scale, rescale and figure height, with mm, cm, m, inches and feet.
Any way you write a scale
1:72, 1/35 and a plain 72 all read as the same scale, and railway names like HO, N, OO and TT work too.
Slicer percentage
Rescale gives the exact percentage, and one click copies it for Bambu Studio, PrusaSlicer or Cura.
Reads your model file
Drop an STL, 3MF or OBJ to read its longest side and get the percentage for a target size.
Drawn to scale
A drawing sets the model beside a 1.8 m adult, so you see the size before you print.
Thin part warning
See how thin a real part can be before it prints thinner than one 0.4 mm line.
Before you rescale a print
Four checks that keep a scaled model printable.
Keep scaling uniform
Lock the axes together in your slicer so the model grows or shrinks without stretching.
Fix inch files first
A model 25.4 times too small or large was saved in inches. Scale it by 2540 or 3.937 percent before anything else.
Thicken fragile parts
Antennas, railings and barrels shrink with the model. Thicken them before you scale down, or print them apart.
Leave the base alone
A 25 mm or 32 mm round base should keep its size when the figure on it changes scale.
Model scale guide
Scale tables, figure scales, slicer steps and nozzle limits in detail.
Common model scales and what they are used for
A scale of 1:N means the model is N times smaller than the real thing in every direction. At 1:24, 24 mm of real car becomes 1 mm of model, so a 4.5 m car prints 187.5 mm long. The bigger the second number, the smaller the model.
The table lists the scales people print most. The last two columns are worked out from a 1.8 m adult and a 4.5 m car, so you can picture each scale before you start a print.
1:6
- Used for
- 12 inch action figures, large busts
- 1.8 m adult
- 300 mm
- 4.5 m car
- 750 mm
1:12
- Used for
- Dollhouses, 6 inch action figures
- 1.8 m adult
- 150 mm
- 4.5 m car
- 375 mm
1:18
- Used for
- Large diecast cars
- 1.8 m adult
- 100 mm
- 4.5 m car
- 250 mm
1:24
- Used for
- Car kits and dioramas
- 1.8 m adult
- 75 mm
- 4.5 m car
- 187.5 mm
1:35
- Used for
- Military vehicles and figures
- 1.8 m adult
- 51.43 mm
- 4.5 m car
- 128.6 mm
1:43
- Used for
- Collector diecast cars, UK O gauge
- 1.8 m adult
- 41.86 mm
- 4.5 m car
- 104.7 mm
1:48
- Used for
- US O scale trains, aircraft kits
- 1.8 m adult
- 37.5 mm
- 4.5 m car
- 93.75 mm
1:56
- Used for
- Vehicles for 28 mm wargames
- 1.8 m adult
- 32.14 mm
- 4.5 m car
- 80.36 mm
1:64
- Used for
- Small diecast cars, S scale trains
- 1.8 m adult
- 28.13 mm
- 4.5 m car
- 70.31 mm
1:72
- Used for
- Aircraft kits, 20 mm figures
- 1.8 m adult
- 25 mm
- 4.5 m car
- 62.5 mm
1:76.2
- Used for
- OO gauge trains (UK)
- 1.8 m adult
- 23.62 mm
- 4.5 m car
- 59.06 mm
1:87
- Used for
- HO scale trains
- 1.8 m adult
- 20.69 mm
- 4.5 m car
- 51.72 mm
1:100
- Used for
- Architecture models, 15 mm wargames
- 1.8 m adult
- 18 mm
- 4.5 m car
- 45 mm
1:144
- Used for
- Airliners and mecha kits
- 1.8 m adult
- 12.5 mm
- 4.5 m car
- 31.25 mm
1:160
- Used for
- N scale trains
- 1.8 m adult
- 11.25 mm
- 4.5 m car
- 28.13 mm
Figure scales: heroic vs true scale
Miniatures are sold by height in millimetres rather than by ratio. A 28 mm figure stands roughly 28 mm from the sole of the foot to the eyes. Some brands measure to the top of the head instead, which is one reason two 28 mm ranges can look mismatched side by side.
Heroic scale exaggerates what matters on a tabletop: heads, hands and weapons are larger and limbs are thicker, so the figure reads well at arm's length and survives handling. True scale keeps real human proportions. Both can be the same height, so a heroic 32 mm figure looks far bulkier than a true scale one.
The table turns figure scales into ratios for a 1.8 m adult under both conventions. Vehicles sold for a figure scale often run a little larger than the strict maths: 28 mm games commonly use 1:56 vehicles and 15 mm games 1:100, which suits chunkier heroic figures.
6 mm
- Measured to the eyes
- 1:280.5
- Measured to the head
- 1:300
- Full height, eyes rule
- 6.42 mm
10 mm
- Measured to the eyes
- 1:168.3
- Measured to the head
- 1:180
- Full height, eyes rule
- 10.7 mm
15 mm
- Measured to the eyes
- 1:112.2
- Measured to the head
- 1:120
- Full height, eyes rule
- 16.04 mm
20 mm
- Measured to the eyes
- 1:84.2
- Measured to the head
- 1:90
- Full height, eyes rule
- 21.39 mm
28 mm
- Measured to the eyes
- 1:60.1
- Measured to the head
- 1:64.3
- Full height, eyes rule
- 29.95 mm
32 mm
- Measured to the eyes
- 1:52.6
- Measured to the head
- 1:56.3
- Full height, eyes rule
- 34.22 mm
54 mm
- Measured to the eyes
- 1:31.2
- Measured to the head
- 1:33.3
- Full height, eyes rule
- 57.75 mm
75 mm
- Measured to the eyes
- 1:22.4
- Measured to the head
- 1:24
- Full height, eyes rule
- 80.21 mm
How to rescale in Bambu Studio, PrusaSlicer and Cura
Slicers scale from the model's current size, so the number you type is a percentage of what is on the plate now. Work it out with the Rescale tab above: a 1:35 model you want at 1:72 needs 48.61 percent. Keep scaling uniform so the model does not stretch.
If a model loads 25.4 times too small or too large, it was saved in inches. Fix that first with 2540 or 3.937 percent, then apply the scale change.
Bambu Studio
- Open the scale tool
- Select the model, press S
- Where to type the %
- The % fields in the scale panel
- Keep it uniform
- Uniform scale on
PrusaSlicer
- Open the scale tool
- Select the model
- Where to type the %
- Scale factors in the Object manipulation panel
- Keep it uniform
- Lock icon closed
Cura
- Open the scale tool
- Select the model, press S
- Where to type the %
- The % fields of the Scale tool
- Keep it uniform
- Uniform scaling ticked
Small scales and your nozzle
Scaling down shrinks every part, including the ones that were thin to begin with. A 0.4 mm nozzle lays lines about 0.4 mm wide, so a wall or rod thinner than that has nothing to print with. Most slicers drop it or print one fragile line.
The table shows how thin a real part can be before it shrinks below one line. At 1:72, anything under 28.8 mm in real life, such as an antenna, a railing or a rifle barrel, ends up thinner than 0.4 mm. A 0.2 mm nozzle halves the limit, and resin printers resolve far finer detail, which is why resin is popular for miniatures.
Thicken fragile parts before you scale, or print them separately. Leave bases out of the rescale too: a 25 mm or 32 mm round base should stay that size when the figure on it changes.
1:24
- Thinnest real part, 0.4 mm nozzle
- 9.6 mm
- Thinnest real part, 0.2 mm nozzle
- 4.8 mm
1:35
- Thinnest real part, 0.4 mm nozzle
- 14 mm
- Thinnest real part, 0.2 mm nozzle
- 7 mm
1:56
- Thinnest real part, 0.4 mm nozzle
- 22.4 mm
- Thinnest real part, 0.2 mm nozzle
- 11.2 mm
1:72
- Thinnest real part, 0.4 mm nozzle
- 28.8 mm
- Thinnest real part, 0.2 mm nozzle
- 14.4 mm
1:87
- Thinnest real part, 0.4 mm nozzle
- 34.8 mm
- Thinnest real part, 0.2 mm nozzle
- 17.4 mm
1:144
- Thinnest real part, 0.4 mm nozzle
- 57.6 mm
- Thinnest real part, 0.2 mm nozzle
- 28.8 mm
1:160
- Thinnest real part, 0.4 mm nozzle
- 64 mm
- Thinnest real part, 0.2 mm nozzle
- 32 mm
Scale calculator FAQ
Answers about the math, slicer percentages, miniatures and railway scales.
How do I calculate model scale?
Divide the real size by the scale number. At 1:24, a 4.5 m (4500 mm) car becomes 4500 ÷ 24 = 187.5 mm. To go back, multiply the model size by the scale number. To find the scale of a model, divide the real size by the model size.
What percentage do I use to change scale in a slicer?
Divide the old scale number by the new one and multiply by 100. A 1:35 model printed at 1:72 needs 35 ÷ 72 × 100 = 48.61 percent. A 28 mm figure printed at 32 mm needs 32 ÷ 28 × 100 = 114.29 percent.
What scale is a 28 mm miniature?
There is no single answer, because 28 mm describes a height, not a ratio. For a 1.8 m adult measured to the eyes it works out to about 1:60, and measured to the top of the head about 1:64. Many 28 mm games use 1:56 vehicles and terrain.
What is the difference between 28 mm and 32 mm heroic scale?
32 mm figures are about 14 percent taller than 28 mm ones, so scaling a 28 mm model by 114.29 percent brings it to 32 mm. Heroic describes proportions rather than size: bigger heads, hands and weapons at any height.
Which scale is HO, N or OO?
HO is 1:87. N is 1:160 (1:148 in the UK and 1:150 in Japan). OO is 1:76.2. O is 1:48 in the US and 1:43.5 in the UK, and G is about 1:22.5. You can type these names straight into the calculator.
Why did small details disappear after I scaled my model down?
Parts thinner than the nozzle's line width cannot print. With a 0.4 mm nozzle at 1:72, anything thinner than about 29 mm in real life ends up under 0.4 mm. Thicken those parts, switch to a 0.2 mm nozzle, or print in resin.