Calculate BIP141 transaction weight, virtual bytes, witness bytes and an estimated fee from base and total serialized sizes.
How it works
BIP141 defines weight as base size × 3 + total serialized size. Virtual size is weight ÷ 4 rounded up. The fee estimate multiplies virtual bytes by the entered sat/vB rate.
The formula
B is the base size without witness, T is the total serialized size including witness, W = 3B + T, vB = ceil(W/4), and fee = ceil(vB × rate).
Worked example
With B=120 bytes and T=220 bytes, W=580 WU and vB=145. At 10 sat/vB the estimated fee is 1,450 sat.
For educational and technical analysis only. Not financial advice, wallet software, transaction signing, or a security audit. Protocol and wallet behavior can differ. Never enter a seed phrase, private key, xprv or wallet password into He-Sab or any website.
Frequently asked questions
What does this calculator calculate?
Calculate BIP141 transaction weight, virtual bytes, witness bytes and an estimated fee from base and total serialized sizes.
Should I enter a seed phrase, private key, xprv or wallet password?
No. These calculators do not need secret wallet material. Never paste a seed phrase, private key, xprv or wallet password into He-Sab or any website.
Is the result authoritative for moving real funds?
No. It is an educational technical estimate. Confirm results with current Bitcoin or Lightning software, specifications and a safe test environment before using real funds.