Apollo 13 passed about 248 miles (400 km) above the Moon at its closest point during the free-return swingby.

Quick Scoop

That’s the commonly cited closest-approach figure for the mission after it was put back onto a free-return path.

Why it matters

  • A free-return trajectory is designed so lunar gravity bends the spacecraft back toward Earth without needing much extra fuel.
  • Apollo 13’s closest lunar pass was high enough to avoid the surface by a wide margin, but still close enough for gravity to send it home.

Tiny nuance

Some sources mention different numbers depending on whether they mean the planned closest approach before the abort or the actual closest approach during the return swingby. The actual swingby after the abort is the roughly 400 km / 248 mile figure.

If you want, I can also give you the closest-approach timeline in hours and minutes from launch.