Should I pre-cut carpet to size?

[happyolly]

I need to replace the carpet in an under stairs cupboard - first time I've done any carpet laying.
Will it be easier if I use the old carpet as a template to cut the new piece to exact size first?
If not, then should I cut to replacement about 30cm bigger? more/less?
Thanks

 

[foxhole]

Template best for small area’s otherwise 70-100mm oversize .

 

[happyolly]

total size is under 2x1m - will cut around the old carpet as a template then following your advice. Thanks