Estimating inference and training time of a neural network on GPU

Hi, I would like to estimate the inference time in a neural network using a GPU. Is there a formula that gives you the inference time knowing the FLOPs of the Neural Network, the number of Cuda Cores and the frequency of the GPU ? Does a similar formula exists for training time ?

Are there other GPU caracteristics that matters in estimating inference or training time ?

Is it reasonnable to estimate that running an inference on a GPU that has 4000 CUDA cores goes twice faster than on a GPU with only 2000 CUDA cores ?