There is no reliable straight answer to this. If you ask a kitchen store, they'll have sources that suggest a huge one. Since you're asking here, my honest answer is, it depends.
What is the age, color, functionality of your current kitchen? If your kitchen is 10 to 15 years old and functional, it may not be much. If your kitchen is 30+ years old and not very functional it may be very high.
Sometimes a minor update returns more than the cost, other times it's a waste of money. I had clients planning on putting granite counters on 35 year old, out of date cabinets. I was convinced whoever bought the house would gut the kitchen and probably reorganize it completely, so that upgrade didn't make sense.
One suggestion if you are planning to sell would be to tour some homes that are in your size, age and price range to see what they have done. Ask an agent or two what they are finding and whether you would be better off leaving the kitchen as is or maybe putting the money into a different area where you would receive a better return.