Interstellar Travel Time Calculator Formula

Understand the math behind the interstellar travel time calculator. Each variable explained with a worked example.

Use the Interstellar Travel Time Calculator

Formulas Used

Travel Time

travel_time_years = distance_ly * 9.461e12 / (velocity_kms * 3.156e7)

Velocity as Fraction of c

fraction_c = velocity_kms / 2.998e5

Variables

VariableDescriptionDefault
distance_lyDistance(light-years)4.24
velocity_kmsCruise Velocity(km/s)60

How It Works

Interstellar Travel Time

At constant velocity, the travel time is simply distance divided by speed.

Formula

t = d / v

  • *d* in light-years (1 ly = 9.461 x 10^12 km)
  • *v* in km/s
  • Result converted to years (1 yr = 3.156 x 10^7 s)

    • Even at 60 km/s (about the speed of the fastest space probe), Proxima Centauri (4.24 ly) would take over 21 000 years.

    Worked Example

    Proxima Centauri (4.24 ly) at 60 km/s.

    distance_ly = 4.24velocity_kms = 60
    1. 01d = 4.24 * 9.461e12 = 4.011e13 km
    2. 02v = 60 km/s = 60 * 3.156e7 km/yr = 1.894e9 km/yr
    3. 03t = 4.011e13 / 1.894e9
    4. 04t = 21 180 years

    Frequently Asked Questions

    What is the fastest spacecraft ever launched?

    Parker Solar Probe, reaching about 200 km/s at closest solar approach. Voyager 1 travels at about 17 km/s relative to the Sun.

    Could we reach another star in a human lifetime?

    Only at a significant fraction of light speed. At 10% c (30 000 km/s), Proxima Centauri would take about 42 years. No current technology achieves this.

    Does relativity matter?

    At a significant fraction of c, time dilation reduces the onboard travel time. At 0.9c, a 4.24 ly trip takes only about 2 years of ship time.

    Ready to run the numbers?

    Open Interstellar Travel Time Calculator