A gas turbine engine comprising: an engine core including, a compressor, a combustor, and a turbine arranged along a reference axis, the turbine configured to drive rotation of a power shaft about the reference axis during operation of the gas turbine engine; a fan driven in rotation about the reference axis by an output shaft; and a gearbox interconnecting the output shaft and the power shaft to transfer rotational energy from the turbine to the fan during operation of the gas turbine engine, the gearbox including (i) a sun gear coupled with the power shaft for rotation about the reference axis with the power shaft, (ii) a plurality of compound gears coupled with the sun gear and spaced circumferentially around the reference axis from one another, each compound gear driven in rotation by the sun gear about a compound-gear axis that is fixed in position relative to the reference axis, and (iii) a ring gear coupled with each of the compound gears and the output shaft to transfer the rotational energy from the plurality of compound gears to the output shaft to drive rotation of the fan; wherein each compound gear includes a first-stage gear coupled with the sun gear, a second-stage gear spaced axially from the first-stage gear and coupled with the ring gear, and a compound-gear shaft interconnecting the first-stage gear and the second-stage gear to cause the first-stage gear and the second-stage gear to rotate together, the first-stage gear and the second-stage gears having diameters (66, 68) that are smaller than a diameter of the sun gear; characterised in that the gearbox includes seven or more compound gears and the ratio of the diameter of the sun gear to the diameter of the ring gear is within a range of 0.2 to 0.6. an engine core including, a compressor, a combustor, and a turbine arranged along a reference axis, the turbine configured to drive rotation of a power shaft about the reference axis during operation of the gas turbine engine; a fan driven in rotation about the reference axis by an output shaft; and a gearbox interconnecting the output shaft and the power shaft to transfer rotational energy from the turbine to the fan during operation of the gas turbine engine, the gearbox including (i) a sun gear coupled with the power shaft for rotation about the reference axis with the power shaft, (ii) a plurality of compound gears coupled with the sun gear and spaced circumferentially around the reference axis from one another, each compound gear driven in rotation by the sun gear about a compound-gear axis that is fixed in position relative to the reference axis, and (iii) a ring gear coupled with each of the compound gears and the output shaft to transfer the rotational energy from the plurality of compound gears to the output shaft to drive rotation of the fan; wherein each compound gear includes a first-stage gear coupled with the sun gear, a second-stage gear spaced axially from the first-stage gear and coupled with the ring gear, and a compound-gear shaft interconnecting the first-stage gear and the second-stage gear to cause the first-stage gear and the second-stage gear to rotate together, the first-stage gear and the second-stage gears having diameters (66, 68) that are smaller than a diameter of the sun gear; characterised in that the gearbox includes seven or more compound gears and the ratio of the diameter of the sun gear to the diameter of the ring gear is within a range of 0.2 to 0.6.