Cubic meters to liters (m3 to L)

One cubic meter is exactly 1,000 liters. The liter is defined as one cubic decimeter, and there are a thousand cubic decimeters in a cubic meter, so the factor falls straight out of the definition with nothing measured.

Worked through: 1 m3 x 1,000 = 1,000 L.

Going the other way, one liter is 0.001 cubic meters.

For mental arithmetic: Add three zeros.

This is the conversion that makes the liter make sense: it is a cube ten centimeters on a side, and a cubic meter is a thousand of them stacked ten by ten by ten. The pairing matters in water billing and in concrete, where volume is ordered in cubic meters and additives are dosed in liters. One cubic meter of fresh water also weighs one tonne, which is the deliberate design of the metric system and the handiest fact in it.

Precision is worth matching to the input. A measurement given as 0.1 m3 carries one or two significant figures, and reporting its conversion to six implies a precision the original never had.