While reading documentation of C-Lightning I found this in section about making onchain transactions with the wallet (funding and withdrawing the wallet):

feerate is an optional feerate to use. It can be one of the strings urgent (aim for next block), normal (next 4 blocks or so) or slow (next 100 blocks or so) to use lightningd's internal estimates: normal is the default. Otherwise, feerate is a number, with an optional suffix: perkw means the number is interpreted as satoshi-per-kilosipa (weight), and perkb means it is interpreted bitcoind-style as satoshi-per-kilobyte. Omitting the suffix is equivalent to perkb.

I am used to sats/vB as this is used by most wallets I know and also by e.g. blockstream.info explorer. What would be equivalent of, lets say, 20 sat/vB in perkw and perkb units?

My understanding is that 1 sat/vB = 1000 perkw, so 20 sat/vB would be 20000 perkw. Is this correct?

1 Answer 1


No, one vbyte [vB] is equal to four weightunits [wu]. The people working on C-Lightning use "sipa" interchangeably for a weightunit.

1,000 sat/kvB = 1 sat/vB
1 sat/vB = 0.25 sat/wu
0.25 sat/wu = 250 sat/kwu

20 sat/vB = 5,000 sat/kwu

Also see: Is there a difference between bytes and virtual bytes (vbytes)?

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