transaction: extend estimated_size() docstring

Extends the docstring of Transaction.estimated_size(). Co-Authored-By: SomberNight <somber.night@protonmail.com>
2026-01-29 16:23:29 +01:00
parent e9ac3e93d7
commit 3133148acd
1 changed files with 8 additions and 1 deletions
@@ -1349,7 +1349,14 @@ class Transaction:
        BIP-0141 defines 'Virtual transaction size' to be weight/4 rounded up.
        This definition is only for humans, and has little meaning otherwise.
        If we wanted sub-byte precision, fee calculation should use transaction
-        weights, but for simplicity we approximate that with (virtual_size)x4
+        weights, but for simplicity we approximate that with (virtual_size)x4.
+        note: while we try to estimate as close to the true value as possible,
+            whenever that's not possible, we should over-estimate. E.g. ecdsa DER sig
+            sizes can be 71 or 72 bytes (even 73 though that is non-standard).
+            Over-estimating is preferred as the typical use-case is the user selecting
+            a target_feerate, and the code calculating abs fees as target_feerate*est_size.
+            If we over-estimate est_size there, that means the final true_feerate is going to
+            be higher than target_feerate, which is desirable especially near the min_relay_fee.
        """
        weight = self.estimated_weight()
        return self.virtual_size_from_weight(weight)