+1000%, minimum..... IF you switched from a Pentium T2310 to an i9-7900X :lol:
In all seriousness though... It depends entirely on the CPUs you're comparing & the workloads they're being compared for.
Take gaming as an example, switching to an i9 from a modern i7-7700K or 8700K, and you're likely losing performance in that given workload.
Productivity that benefits more from cores than clockspeed, could well be +50% or more.