How big and how thick are Saturn's rings?

Updated October 19, 2026 · 5 min read

Saturn's main rings measure about 280,000 km (175,000 miles) from edge to edge, nearly three-quarters of the distance from Earth to the Moon, and span about 73,000 km from their inner edge out to the F ring. Their thickness, by contrast, is usually only about 10 meters (30 feet), exceeding a kilometer in just a few places. Their total mass, measured by Cassini in 2017, is about 1.5 × 10¹⁹ kg, roughly 40% of the small moon Mimas.

Rings wider than the planet

Ring distances are measured from Saturn's center; the planet's equatorial radius is 60,268 km. The D ring begins about 6,600 km above the cloud tops, and the A ring's outer edge lies 136,775 km from the center. Edge to edge, the bright rings span about 2.3 times the planet's diameter.

Include the faint rings and the scale explodes: the E ring, fed by Enceladus, reaches about 480,000 km from Saturn's center, and the Phoebe ring about 16 million km. For ring-by-ring details, see ring names; for the planet itself, see Saturn's size and mass.

Astonishingly thin

The local thickness of the main rings is estimated at about 10 meters, sometimes a few tens of meters. That figure comes from how density and bending waves raised by moons propagate, which depends on how agitated the particles are, and from stellar occultations observed by Cassini.

The ratio of width to thickness has no everyday equivalent. Ten meters of thickness against 280,000 km of diameter is about 1 part in 28 million. A sheet of paper 0.1 mm thick, scaled to the same proportions, would be nearly 3 km (2 miles) wide.

Collisions explain the thinness. Particles that stray from the equatorial plane cross it twice per orbit and bump into others. Each impact dissipates a little energy, so vertical motion is damped and the disk flattens. The plane stays aligned with Saturn's equator, enforced by the planet's equatorial bulge.

Mountains in the rings

The rings are not perfectly flat. The August 2009 equinox offered a unique test: sunlight struck the rings edge-on, so anything sticking out of the plane cast a long shadow. Cassini revealed:

• structures up to about 2.5 km high along the B ring's outer edge, where the resonance with Mimas stirs the particles;
• vertical waves about 1.5 km high along the edges of the Keeler Gap, raised by Daphnis;
• the shadows of propellers, disturbances created by small moonlets embedded in the A ring (see shepherd moons).

Other distortions are broader but lower. The C and D rings carry spiral corrugations, like corrugated sheet metal, attributed to a cloud of comet debris striking them in the early 1980s. These findings also explain why older Earth-based measurements made during edge-on passages suggested apparent thicknesses of about a kilometer: they mostly saw such structures, the F ring and the dusty rings.

How much do the rings weigh?

Until 2017 the ring mass was poorly known. On the final orbits of its Grand Finale, Cassini flew between Saturn and the rings, which made it possible to separate their pull from the planet's by tracking the spacecraft's path precisely. The result, published in 2019 by Luciano Iess's team: 1.54 × 10¹⁹ kg, with an uncertainty of about a third.

To picture that mass:

• it equals about 40% of the mass of Mimas, a moon less than 400 km across;
• gathered into a ball of ice, it would make a body about 320 km in diameter;
• it is roughly 1% of the mass of Earth's oceans.

Most of it is concentrated in the dense B ring. This low mass relative to the rings' huge area is one argument for young rings (see ring age and origin).

As seen from Earth

At opposition, Saturn's globe measures about 19 arcseconds across and its rings about 40 to 45 arcseconds: more than twice as wide as the planet, which makes them visible from about 25 to 30 times magnification. Their look changes with our viewing angle, from nearly invisible edge-on, as in 2025, to a maximum opening of about 27° (see disappearing rings).

Sources

• L. Iess et al., "Measurement and implications of Saturn's gravity field and ring mass," Science, 2019
• NASA Science, Saturn
• J. N. Cuzzi et al., "An evolving view of Saturn's dynamic rings," Science, 2010
• L. W. Esposito, Planetary Rings, Cambridge University Press, 2014