# Map Features/Units

Some tags have measurable values. The unit of such a value can be given explicitly as part of the value (e.g. maxspeed=50 mph). If no unit is specified, a default unit will be assumed (e.g. for maxspeed=50, the unit kilometre per hour is assumed). If the unit is different from the default, e.g. in non-metric countries, stating an unit is obligatory.

This article shows which units can be explicitly specified and which default units are implicitly assumed.

## Default units

If no unit is explicitly specified, the following units are assumed:

Measure Default unit Implicit specification Example
Length Metre (meter) `m` width=3 means a width of 3 metres
Distance Kilometre (kilometer) `km` distance=5 means a distance of 5 kilometres
Speed Kilometres per hour `km/h` maxspeed=100 means a speed limit of 100 kilometres per hour
Weight Tonne (metric ton) `t` maxweight=3.5 means a weight limit of 3.5 tonnes (3500 kg)

## Explicit specifications

The following units can be explicitly specified by adding them after the numeric value, separated by a space (with the exception of the combined specification of feet and inches):

Measure Explicit specification Unit Example Aliases (Highly Discouraged) Conversion to default unit
Length or Distance
`m` Metre (meter) height=3 m metre, metres,
meter, meters
-
`km` Kilometre (kilometer) width=0.2 km kilometre, kilometres,
kilometer, kilometers
Multiply by 1000 or divide by 0.001
`mi` Mile width=1.45 mi mile, miles Multiply by 1609.344 or divide by 0.000621371192
`nmi` Nautical Mile distance=6 nmi international nautical mile Multiply by 1852
<feet>`'`<inch>`"` Feet and inches combined maxwidth=12'5" ft in Multiply the feet by 12, add the inches and multiply the result by 0.0254
Speed
`km/h` Kilometres per hour minspeed=80 km/h kph, kmph -
`mph` Miles per hour maxspeed=60 mph Multiply by 1.609344
`knots` Knots maxspeed=10 knots Multiply by 1.852
Weight
`t` Tonne (metric ton) maxweight=3 t -
`kg` Kilogram (kilogramme) maxweight=3500 kg - Divide by 1000

## Common mistakes

The following table presents examples of incorrect or discouraged tag usage together with their correct notation.

Incorrect usage Explanation Correct usage
`height=6m` Missing space between numeric value and unit. height=6 m
`maxweight=3,5` Comma used as decimal separator. maxweight=3.5
`width=12' 6"` There should be no space between the specification of feet and inches. width=12'6"
`maxspeed=50 kph` Usage of an alias. maxspeed=50 km/h