HO Scale Calculator

HO is the most popular model railroad scale in the world, running on 16.5 mm gauge track at a ratio of 1:87.1. At HO scale, a 87 cm real measurement becomes about 1 cm on the model.

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What fits at 1:87.1 (1:87)

Model railroads, trackside buildings, vehicles and figures. The huge HO ecosystem makes almost any prototype available.

Real subjectReal size1:87.1 model
40 ft boxcar 12.2 m 14 cm
EMD F7 locomotive 15.4 m 17.7 cm
Two-storey house (height) 8 m 9.2 cm
Person 1.8 m 2.1 cm

Size comparison at 1:87.1

Relative model sizes at 1:87.1 (longest bar = largest model):

1:87.1 in mm, cm and inches

How common real-world sizes convert to 1:87.1 model size:

Real sizeModel (mm)Model (cm)Model (inches)
1 m 11.5 mm 1.15 cm 0.452 in
2 m 23 mm 2.3 cm 0.904 in
5 m 57.4 mm 5.74 cm 2.26 in
10 m 115 mm 11.5 cm 4.52 in
1 ft 3.5 mm 0.35 cm 0.138 in
6 ft (person) 21 mm 2.1 cm 0.827 in

Frequently asked questions

What scale is HO?

HO is 1:87.1, running on 16.5 mm gauge track. It is the most widely produced model railroad scale.

How tall is an HO figure?

A 1.8 m person is about 20.7 mm tall in HO scale (1800 mm ÷ 87.1).

Related scales

→ See all scales