This is a very common tree-surgery practice. Usually specified in metres, although sometimes as a percentage.
So you now have had the tree cut down. You’re left with a stump that is likely to be 3 or 4 inches above ground level. What now?
Well that all depends on the plan for the bit of ground the tree lived on. Quite often tree stumps are just left there to rot down and covered with bark. The decomposition process takes a long time (around 9 or 10 years) but quite kindly mother nature will provide this service free of charge!
Your other options are digging with a machine or using a stump grinder. A stump grinder is usually the better option as it creates the least mess in the process.
A Stump grinder has a toothed wheel that spins at high revolutions and chips away at the stump. The machines themselves vary in size from small pedestrian machines on wheels (that are pushed in by hand) to self propelled machines on wheels and heavier duty machines on tracks.
In the UK the pedestrian machines and the tracked machines are both quite popular as they offer access into most gardens.
The heavier duty wheeled machines tend to be quite wide and can struggle through gateways.
How do we determine how much of the tree stump needs removing?
When we measure a stump we measure the widest part of the stump and then add a third on to that to allow for the flares of the stump underground. Stumps can be ground to a shallow level such as that required to let grass grow over it or then can be ground out much deeper if required for the ground to be developed or slabbed over.