Owlracle API uses the average gas used in the recent blocks to calculate the estimated fee.
So if the fee is:
gas price (in ether) * gas amount * ETH price
And if we are getting 90.73 GWei
for fast speed, $7.72
for an estimated fee, $1037
ETH price (at the time of your question), that means that at the time of the estimations, the average gas used was 7.72 / (90.73^-9 * 1037) =~ 82051
.
You can use Owlracle API to get all kinds of gas related information, like the average gas used to perform the fee calculation.
At the time of my writing, this is the response I got from /gas endpoint:
{
"timestamp":"2022-07-26T18:52:11.505Z",
"lastBlock":15219809,
"avgTime":14,
"avgTx":208.08,
"avgGas":77433.83295590722,
"speeds":[{
"acceptance":0.355,
"gasPrice":16,
"estimatedFee":1.7002611305126285
},{
"acceptance":0.6,
"gasPrice":19.835912411,
"estimatedFee":2.1078894287922707
},{
"acceptance":0.9,
"gasPrice":26.272281325,
"estimatedFee":2.7918586716743947
},{
"acceptance":1,
"gasPrice":32.092197568,
"estimatedFee":3.4103197573501443
}],
"baseFee":17.338222816440013
}