If you’ve withdrawn BTC through the non-custodial wallet, you might have noticed that fees can seem a bit high at times.
Why do BTC transaction fees vary?
Bitcoin transactions are made up of inputs (the amount of transactions you've received) and outputs (where the funds are going). The bigger the transaction, the higher the fee. Transaction size is measured in weight units (WU), and this size directly affects how much you’ll pay in fees.
1 input = 1 previous incoming transaction. The more inputs a transaction has, the more data is needed to process it, making it heavier.
Why are fees higher than on my other non-custodial wallet?
When you withdraw BTC from your Sellix wallet, the transaction often includes lots of inputs. This is because each invoice or payment you receive creates a separate input. If you’re sending a large amount that’s made up of smaller payments, the transaction size gets bigger due to the many inputs.
Transaction A - This diagram shows how multiple inputs combine into a single output, increasing transaction size and, therefore, fees.
Example: High transaction weight
A quick comparison of two transactions with different weights:
Transaction A (Higher Weight):
Weight: 19.50 kWU
Fee: $35
Fee rate: 18 sat/vbyte
Inputs: ~40 smaller payments
Transaction B (Lower Weight):
Weight: 1.50 kWU
Fee: $2
Fee rate: 18 sat/vbyte
Inputs: 3 combined payments
Even though the fee rate (sat/vB) was identical for both transactions, Transaction A incurred much higher fees because its size (weight) was significantly larger due to the number of inputs.
Transaction B - Fewer inputs combined, thus resulting in a lower TX fee.
How to Keep Fees Low
A couple of tips:
Avoid letting small payments accumulate for too long before withdrawing. You can make occasional consolidation transactions by sending all of the transaction inputs in your wallet back to yourself in one transaction. This combines the smaller inputs into one larger input at a new address, reducing the size and cost of future withdrawals. This makes future transactions smaller and cheaper.
Try withdrawing during off-peak times to benefit from lower fee rates. We suggest using https://mempool.space as a source for current BTC fee rates.
Further questions?
If you need help or have any questions, reach out via the chat widget or email us at support@sellix.io.