Orbital period calculator
Using Kepler’s third law, T = 2π·√(a³ / GM), this tool finds how long one orbit takes from the central mass and the orbit’s semi-major axis.
Pick the Sun, Earth or Jupiter as the central body, or enter your own mass, then set the semi-major axis in kilometres (1 AU ≈ 149,597,870 km). The period is shown in days, years and seconds — all computed in your browser.