Your phone's GPS would drift by miles per day if Einstein's relativity were not baked into the satellites. Special relativity says a moving clock ticks slower as seen by a stationary observer: the observed time equals the clock's own proper time multiplied by the Lorentz factor, Δt = Δt₀ × γ, where γ = 1/√(1 − v²/c²). At everyday speeds γ is essentially 1 and nothing looks strange; at 87% of light speed γ hits 2 and the moving clock runs at half rate.

This calculator applies the time-dilation multiplication. Type the proper time — the time measured by the moving clock itself — into Variable A, and the Lorentz factor γ for your velocity into Variable B; the Result box gives the dilated time seen by the stationary observer. GPS engineers live this daily: the satellites' clocks tick faster from weaker gravity and slower from orbital velocity, netting a 38-microsecond-per-day correction without which your position would wander. Particle physicists at Fermilab watch the same effect stretch a muon's 2.2-microsecond life long enough to reach their detectors.

With the pre-filled defaults — Variable A 10, Variable B 5 — the Relativity Calculator returns Result 50.0000. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.