Bitcoin Transaction Fees - Everything in one.
Transaction fees and fee rates (Learn me a Bitcoin).

Bitcoin transaction fee is from transaction size and fee rate used for it, so these two Bitcoin transaction size calculators can help too.
https://jlopp.github.io/bitcoin-transaction-size-calculator/
https://bitcoinops.org/en/tools/calc-size/

Lastly, this calculator and tool to plot your Bitcoin transaction in Bitcoin mempools is helpful for learning and practicing too.
https://bitcoindata.science/plot-your-transaction-in-mempool