Lightning vs on-chain:
when does each make sense?

This tool runs entirely in your browser: no data is sent to any server. The BTC price field starts at $81,262, the Coin Metrics end-of-day USD price for 2026-09-19 in the site's data snapshot^[2], and is replaced by the saved daily close when the site's data file loads, unless you have typed your own price or opened a share link that carries one. Only a typed or shared price is saved in your browser, so on a later visit the field shows the latest saved close. Clearing the field hands it back to that close the next time the page loads. Without a price above $0, sats and BTC amounts are still compared in sats and the USD figures are left blank; a USD amount needs a price to convert.

The amount is converted to sats first: BTC × 100,000,000, or USD ÷ price × 100,000,000. The amount, fee rate, base fee and ppm each take 0 or more; a blank or negative value shows no result until it is fixed, and the verdict names the field.

• On-chain fee = 141 vB × fee rate (sat/vB). 141 vB is a one-input, two-output native SegWit payment: 10.5 vB overhead + 68 vB input + 2 × 31 vB outputs = 140.5, rounded up. Virtual size is transaction weight ÷ 4, where witness bytes count once and all other bytes four times^[3]. The fee does not depend on the amount sent. The fee rate is used exactly as entered, 0 included (default 20 sat/vB).
• Lightning fee = base fee + amount × ppm ÷ 1,000,000, the per-channel fee formula in the Lightning routing spec^[4], charged once. Defaults: 1 sat base fee, 100 ppm.
• USD fee = sats ÷ 100,000,000 × price. Both fees are rounded to whole sats; the lower rounded fee wins, and the amount saved is the difference between the two rounded fees (converted to USD at the same price). Fees that round to the same number of sats are shown as a tie.
• Crossover amount = (on-chain fee - base fee) × 1,000,000 ÷ ppm. Lightning is cheaper below it, on-chain above it. None is shown when ppm is 0 or the base fee is at least the on-chain fee, because then the fees never cross.

Not modeled: fees added by each extra hop on a multi-hop route, the on-chain cost of opening or closing a channel, failed payments on large amounts, and on-chain spends with more inputs or other address types.

Verify the methodology or inspect the source code in your browser's dev tools.