Eratosthenes Simulator

Pick two cities roughly north–south of each other. The Sun's noon altitude in each city and the distance between them give you the circumference of the Earth.

Distance to use

City A

City B

Suggested partners for City A

    Choose two cities to see the measurement.

    Your trials

    Each time you press Calculate, the result is added here. Compare your trials with the reference charts below.

    Reference: accuracy vs. longitude difference

    Computing reference pairs…

    Reference: accuracy vs. distance apart

    Computing reference pairs…