This site https://jochen-hoenicke.de/queue/#2h helps me a lot.

Steps to ensure fastest send.
1. These times you can never be sure of the fees to pay. So I strongly advice that whenever you send, you make sure to opt-in RBF (replace-by-fee) transactions.
2. Go check https://jochen-hoenicke.de/queue/#2h Right now it says there are 1,100 pending TX for 280+ sats per byte.
3. Check https://tradeblock.com/bitcoin/ to find out how much TX was included in the last 4 blocks and when was the last block found.
4. Determine the size of your send by using https://coinb.in/#newTransaction
5. Let's say 382 bytes is the final size of your tx. That's 0.0010696BTC.

From the above steps, you can approximate how much fees to pay.