---
title: "Model Scale Converter: HO, N, OO, 1:35, 1:72 | Diorama Fern"
description: "Convert real sizes to model sizes and back at HO, N, OO, O, 1:35, 1:72, 28 mm figure or 1:12 dollhouse scale, in mm, cm and inches, with cited ratios."
url: https://dioramafern.me/
---

mm · cm · inches · feet

# Model scale converter

Real size to model size and back, at any railway, kit, figure or dollhouse scale.

## How the converter works

A scale of 1:87.1 means everything on the model is 87.1 times smaller than the real thing. **Divide a real size by the scale number to get the model size**, and multiply a measurement off the model to get the real one. Type in either box and the other follows, in millimetres, centimetres and inches, with feet for real sizes. The quick reference shows a person, a door, a storey and a car at the scale you chose.

Model railway ratios come from the standards bodies: the NMRA for North America and MOROP's NEM standards for Europe. They mostly agree, but not everywhere. HO is 1:87.1 for the NMRA and H0 is 1:87 in NEM 010, which also calls it 3.5 mm scale (3.5 mm to the foot). O is 1:48 for the NMRA, while NEM 010 makes 0 1:45 and notes that 1:43.5 (7 mm to the foot) is also used in some countries. The NMRA's OO is 1:76.2, where NEM 010 calls 4 mm scale 1:76.

Kit scales such as 1:35, 1:48, 1:72 and 1:24 are conventions rather than standards: they are the scales kit makers sell their ranges in. Dollhouse scales, 1:12 (one inch to the foot) and 1:24 (half an inch), are miniaturists' conventions.

### Figure scales in millimetres

Wargaming and figure scales such as 28 mm or 54 mm give a figure's height, not a ratio, and makers measure it differently: some to the eyes, some to the top of the head, and sculpted proportions vary too. Taking an average man from NASA's anthropometric data (68.7 in, or 1.745 m, tall with his eyes at 64.7 in), a 28 mm figure works out at about 1:59 measured to the eyes and 1:62 to the top of the head. The converter uses the middle of that range, so treat figure scales as approximate.

| Scale | Ratio | 1 real foot | Basis | Notes |
| --- | --- | --- | --- | --- |
| Z | 1:220 | 1.39 mm | NMRA S-3.2 and NEM 010 | 6.5 mm track |
| N | 1:160 | 1.91 mm | NMRA S-3.2 and NEM 010 | 9 mm track |
| TT | 1:120 | 2.54 mm | NMRA S-3.2 and NEM 010 | 12 mm track |
| HO | 1:87.1 | 3.5 mm | NMRA S-3.2 | 3.5 mm to the foot, 16.5 mm track |
| H0 | 1:87 | 3.5 mm | NEM 010 | 16.5 mm track |
| OO | 1:76.2 | 4 mm | NMRA S-3.2 (NEM 010: 4 mm scale, 1:76) | 4 mm to the foot |
| S | 1:64 | 4.76 mm | NMRA S-3.2 and NEM 010 | 3/16 in to the foot, 22.5 mm track |
| O | 1:48 | 6.35 mm | NMRA S-3.2 | 1/4 in to the foot |
| 0 | 1:45 | 6.77 mm | NEM 010 | 32 mm track |
| O (7 mm) | 1:43.5 | 7.01 mm | NEM 010 note (some countries) | 7 mm to the foot |
| 1 | 1:32 | 9.53 mm | NEM 010 (gauge I); in NMRA large scale | Gauge 1, 45 mm track |
| Large scale 1:29 | 1:29 | 10.51 mm | NMRA S-3.2 large scale | Garden railways on 45 mm track |
| II (G) | 1:22.5 | 13.55 mm | NEM 010 (II); in NMRA large scale | Garden railways, metre gauge on 45 mm track |
| F (Fn3) | 1:20.3 | 15.01 mm | NMRA S-3.2 | 3 ft narrow gauge on 45 mm track |
| 1:32 | 1:32 | 9.53 mm | Kit convention | Aircraft |
| 1:35 | 1:35 | 8.71 mm | Kit convention | Military vehicles and figures |
| 1:48 | 1:48 | 6.35 mm | Kit convention | Aircraft and military |
| 1:72 | 1:72 | 4.23 mm | Kit convention | Aircraft |
| 1:76 | 1:76 | 4.01 mm | Kit convention | Military vehicles, close to OO |
| 1:144 | 1:144 | 2.12 mm | Kit convention | A kit scale in the Airfix range |
| 1:350 | 1:350 | 0.87 mm | Kit convention | Ships |
| 1:700 | 1:700 | 0.44 mm | Kit convention | Waterline ships |
| 1:12 | 1:12 | 25.4 mm | Kit convention | Motorcycles and big racing cars |
| 1:20 | 1:20 | 15.24 mm | Kit convention | Grand Prix cars |
| 1:24 | 1:24 | 12.7 mm | Kit convention | Cars |
| 1:43 | 1:43 | 7.09 mm | Kit convention | A kit scale in the Airfix range |
| 6 mm figures | about 1:282 | 1.08 mm | Approximate: makers measure differently | Wargames |
| 10 mm figures | about 1:169 | 1.8 mm | Approximate: makers measure differently | Wargames |
| 15 mm figures | about 1:113 | 2.7 mm | Approximate: makers measure differently | Wargames |
| 20 mm figures | about 1:85 | 3.6 mm | Approximate: makers measure differently | Wargames |
| 28 mm figures | about 1:61 | 5.04 mm | Approximate: makers measure differently | Tabletop wargames |
| 32 mm figures | about 1:53 | 5.76 mm | Approximate: makers measure differently | Tabletop wargames |
| 54 mm figures | about 1:31 | 9.72 mm | Approximate: makers measure differently | Display figures |
| 75 mm figures | about 1:23 | 13.49 mm | Approximate: makers measure differently | Display figures |
| 1:12 | 1:12 | 25.4 mm | Miniaturist convention | One inch to the foot, the usual dollhouse scale |
| 1:24 | 1:24 | 12.7 mm | Miniaturist convention | Half inch to the foot |
| 1:48 | 1:48 | 6.35 mm | Miniaturist convention | Quarter inch to the foot |
| 1:144 | 1:144 | 2.12 mm | Miniaturist convention | A dollhouse for a 1:12 dollhouse |

## Sources

- North American railway scales (O 1:48, S 1:64, OO 1:76.2, HO 1:87.1, TT 1:120, N 1:160, Z 1:220, F 1:20.3, and large scale on 45 mm track at 1:32, 1:29, 1:24, 1:22.5 and 1:20.3): [NMRA Standard S-3.2, Track, Standard Scale](https://www.nmra.org/sites/default/files/standards/sandrp/Mech/S/s-3.2_track_standard_scale.pdf) (28 June 2026). Its list of scales was formerly in [NMRA S-1.2, Standard Scales](https://www.nmra.org/sites/default/files/standards/sandrp/General/S/s-1.2_standard_scales.pdf), which since May 2026 points to S-3.2.
- European railway scales and gauges (Z 1:220, N 1:160, TT 1:120, H0 1:87, S 1:64, 0 1:45, I 1:32, II 1:22.5; 1:43.5 also used for 0 in some countries; 4 mm scale 1:76 and 7 mm scale 1:43.5): [MOROP NEM 010, Scales, Nominal Sizes, Gauges](https://www.morop.org/images/NEM_register/NEM_E/nem010_en_2011.pdf) (2011).
- Kit scales are industry conventions; for example, the series in Tamiya's range (1/12 motorcycles, 1/20 Grand Prix, 1/24 sports cars, 1/32 and 1/48 aircraft, 1/35 and 1/48 military, 1/72 aircraft, 1/350 and 1/700 ships), listed in the menu of its [English product pages](https://www.tamiya.com/english/products/35223/index.html), and the scales on [Airfix's shop by scale](https://uk.airfix.com/shop/scale) (including 1:24, 1:32, 1:35, 1:43, 1:48, 1:72, 1:76, 1:144 and 1:350).
- Dollhouse scales 1:12 (one inch to the foot), 1:24 (half inch), 1:48 (quarter inch) and 1:144: [About Miniature Scales](https://cincy-miniatures.org/index.php/about-miniature-scales/), The Miniature Society of Cincinnati (a club of the National Association of Miniature Enthusiasts).
- Figure heights measured to the eyes by some makers and to the top of the head by others: Wikipedia, [Miniature figure (gaming)](https://en.wikipedia.org/wiki/Miniature_figure_(gaming)), used here because no standards body defines figure scales.
- Average man's stature 68.7 in and standing eye height 64.7 in: NASA Reference Publication 1024, Anthropometric Source Book (1978), as tabulated in the US Department of Defense's [Anthropometric Guidelines](https://www.denix.osd.mil/ergo-wg/denix-files/sites/58/2016/04/AnthropometricGuidelines.doc).
- Inch (25.4 mm) and foot (0.3048 m): [NIST Handbook 44](https://www.nist.gov/pml/owm/nist-handbook-44-current-edition), Appendix C.

## More for the workbench

Print it, resize it, lay the track, plant the jar.

- [Printable scale ruler](https://dioramafern.me/scale-ruler/): A ruler marked in real metres and feet for any scale, with a calibration bar.
- [Scale-to-scale converter](https://dioramafern.me/scale-to-scale-converter/): The photocopy percentage from 1:35 to 1:72, and which scale a figure fits.
- [Gradient & helix calculator](https://dioramafern.me/model-railway-gradient-calculator/): Rise and run to % and 1 in N, minimum curve radius, and helix height per turn.
- [Terrarium calculator](https://dioramafern.me/terrarium-calculator/): Container volume and every layer in litres and US quarts, with bags to buy.
- [Terrarium plant picker](https://dioramafern.me/terrarium-plant-picker/): Plants for open or closed terrariums by light and height, each with its source.

## Recommended

Two free services for the online side of the hobby.

Temporary email · no sign-up

### CleanTempMail

Free paper kits, printable textures and build guides often sit behind a sign-up form, and the newsletters keep coming long after the download. CleanTempMail gives you a free temporary inbox straight away: no sign-up, a random or custom address on hundreds of domains, and messages deleted automatically after 3 days. Use your real address for kit orders and anything you need a receipt for.

[Get a temporary inbox](https://cleantempmail.com/)

Disposable cloud browser · domain lookups

### WebTraceCheck

Spotted a rare kit or a long-gone locomotive at a surprisingly low price on a shop you have never heard of? WebTraceCheck's free DNS and domain lookup shows how long a site's domain has existed, and its disposable cloud browser opens unfamiliar links on an isolated desktop that is deleted after each session. Nothing to install, with free time every day.

[Try WebTraceCheck](https://webtracecheck.com/)

## Questions

**What is the difference between HO and H0?**

They run on the same 16.5 mm track at almost the same scale. The NMRA defines HO as 1:87.1, and MOROP's NEM 010 defines H0 as 1:87, or 3.5 mm to the foot. The difference is about a tenth of a percent: a 10 m wagon is 114.8 mm long in HO and 114.9 mm in H0.

**Is 1:72 the same as 1:76 or OO?**

No. 1:76 is 4 mm to the foot, the scale of British OO (the NMRA gives OO as 1:76.2), while 1:72 is the common aircraft and armour kit scale. A 1:72 model is about 5.5% bigger: a 1.8 m person is 25.0 mm tall at 1:72 and 23.7 mm at 1:76.

**What scale is a 28 mm figure?**

There is no single answer, because makers measure figures differently. For an average man, a 28 mm figure works out at about 1:59 if measured to the eyes and about 1:62 if measured to the top of the head, and ranges from different makers vary in build and height, so compare figures side by side before mixing them.

**How do I convert a real measurement to a model one?**

Divide it by the scale number. A 12 m coach in N scale (1:160) is 12,000 ÷ 160 = 75 mm long; in HO (1:87.1) it is 137.8 mm. To go the other way, multiply the model measurement by the scale number.