The common sizes for garden trampolines are 8ft, 10ft, 12ft and 14ft. There are of course many other sizes available both larger and smaller and oval shaped garden trampolines.
The size of trampoline you purchase is dependent on many factors including the space available in your garden, your budget and who is actually going to use the trampoline.
A range of trampolines to suit different size and budget requirements can be viewed at www.trampolinesonline.co.uk
As the size of the trampoline increases you generally find that the maximum weight limit also increases, as an example the 8ft Telstar jump capsule package has a maximum user weight of 90kg whereas the 14ft trampoline Telstar jump capsule package has a maximum weight limit of 130kg.
As a general rule is advisable to buy a lager trampoline than you currently need, this is especially true if you have young children as the additional size of the trampoline will become beneficial as your children grow.