# Roblox Units

This article outlines Roblox physical units and how they convert to metric units. Understanding units is useful whenever you work with physics, as in the following examples:

## Unit Conversions

In general, you can use the conversions in the following table to relate Roblox's primary units for time, length, and mass to their metric counterparts.

UnitRobloxMetric
Time1 second1 second
Length1 stud28 cm
Mass1 RMU*21.952 kg

## Importance of Unit Consistency

Internally, the Roblox physics engine does not use unit conversions. You're free to define your own unit interpretations for studs (length) and RMUs (mass), but these should be used in a consistent manner throughout the experience. For example, if you decide that one stud equals one foot (30.483 cm), the unit density of water implies an RMU is equal to 62.4 lbs (28.3 kg):

1 (g/cm³) × (30.48³ cm³/ft³) = 28,317 (g/ft³) × (0.00220462 lbs/g) = 62.4 (lbs/ft³) = 1 (RMU/stud³)

Overall, it's recommended that you use standard Roblox units because it makes an experience work as expected in all scenarios, such as compatibility with VR controls.