What is a stere of firewood ?

The stere is the only unit of international recognition. It is a quantity of wood 1 meter in length contained within a 1m by 1m by 1m  cube.

However, be aware that, if the stere of 1 meter in length is cut into 50cm, 33cm or 25cm logs, then the volume of the stere will be lower although the weight remains the same.

The initial stere consists of logs 1 meter in length,
and  by definition, fills a volume of 1 cubic meter.

Once the logs are cut to a length of 0.5 meters,
the volume is reduced to 0.8 cubic meters.

If the logs are cut to a length of 0.33 meters,
the volume is further reduced to 0.7 cubic meters.