Length Contraction Calculator
Works out the shortened length of something moving at relativistic speed.
Measured length while moving
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Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
Lorentz factor (γ) —
Shorter by —
Speed —
Reading this —
The formula
L = L₀ ÷ γ γ = 1 ÷ √(1 − v²/c²)
L₀ is the length measured at rest relative to the object.
What to watch out for
The object’s own crew sees nothing unusual: its length only changes for an observer it moves past.
Frequently Asked Questions
How long is a 100 m ship at 90% of light speed?
43.59 m, as measured by someone it passes.
What about at 99.9%?
4.47 m.