It's interesting that other sources cite an even higher number:
$19 trillion in transactions settled on the Bitcoin network in 2024 (Cointelegraph)
This wasn't even the record volume according to that source, which was recorded in 2021, with 47 trillion.
As the average BTC/USD price in 2021 was probably lower than in 2024, this looks strange at a first glance. However, in 2024 a lot of block space was occupied by Ordinals and Runes transactions, at least in the first half of the year. This in addition to the reduced block reward due to the 2024 halving (reward payments are also "transactions") could be the reason for that difference.
I looked at the
output volume chart on Blockchain.com to understand a bit better what was going on:
- Output volume before the halving was roughly at 750,000 and 1,100,000
BTC per day. 99,000 of them (or 900 per day) were block rewards.
- After the halving it fell to 600,000 to 850,000
BTC per day. 450 per day were block rewards.
- This of course includes change, but we can't tell with certainty how much went to change addresses and thus are not really "payments".
- It also contains output consolidations, CoinJoins, mixing and similar stuff.
I guess the Coinmetrics 6.6 trillion number are an estimation for "payments not including change", while 19 trillion may be the raw value of all outputs, without change and block rewards. At least looking at the figures in BTC from Blockchain.com (the 600k to 1,1M BTC per day), the order of magnitude of the "output value" numbers gets close to the 19 trillion, while the Coinmetrics value is much lower.