It is not percentage based but based on the demand for the next block space. That demand is on the basis who will pay the most per byte for each transaction so your is based on the number of bytes in your transaction (usually directly proportional to the number of inputs and outputs) and how quickly you want it in the next block. Currently about 44 cents will guarantee you in the next block - note this is a moving target based on the competition for block space. mempool.space is a good visualisation.