Bitcoin fees depend on the size of the transaction. For a bigger size of transaction, you must have to pay higher transaction fee. Here bigger size don't refer to the amount of the bitcoin to be transacted.

How to calculate transaction size
Source

Input*180 + output*34 + 10 plus or minus input
Say, input is 2 and output is to 3 address. The size is-
2*180 + 3*34 + 10 + or - 2 = 474/470bytes.

Input= number of times received bitcoin on an address.
Output= number of addresses where you will send.

When input and output increase, the total size will also be increased which will cause you higher fee.

How to calculate fees
Now that the transaction size is calculated, check bitcoinfees and find out the current amount of satoshi per byte.
According to this site-
If someones pay 62 satoshi per byte, the transaction will likely to be listed in the next block, however, it's possible to pay less fee which will cause slow confirmation. If more fee is paid, the transaction process will be more faster.