Potting compost in Litres?

[pinstripe]

Why although sold as a solid entity is potting compost sold in litres and not by weight?

[Hymie]

What most people fail to appreciate that a Litre is a measure of volume � because most liquids are measured by volume, people seem to think it only applies to liquids.

The main reason for compost to be sold by volume rather than weight is that the moisture content will have a significant effect on the weight, but to a lesser extent the volume.

[heathfield]

It lets you know how many pots of a given volume you can fill, rather than how heavy they're going to be.