Exact, not approximate
The unit converter does whole-number arithmetic in satoshis, so 0.1 + 0.2 BTC is exactly 0.3 BTC — never 0.30000000000000004.
AUX/04 — auxiliary tools for bitcoin
Small calculators.
No accounts. No network.
The arithmetic around Bitcoin — units, fees, block heights, address formats — done in your browser. Save the page and it keeps working without a connection.
Unit converter
Type in any field; the others follow. Conversions are exact — no floating-point rounding.
BTC
mBTC
bits
sats
| 1 BTC | 1,000 mBTC · 1,000,000 bits · 100,000,000 sats |
|---|---|
| 1 mBTC | 0.001 BTC · 100,000 sats |
| 1 bit | 0.000001 BTC · 100 sats |
| 1 sat | 0.00000001 BTC — the smallest on-chain unit |
Fee estimator
Estimate a transaction's virtual size, then multiply by the fee rate your wallet or a block explorer suggests.
sat/vB
Typical sizes: legacy input 148 B, output 34 B, overhead 10 B; native SegWit input 68 vB, output 31 vB; Taproot key-path input 57.5 vB, output 43 vB; SegWit overhead 10.5 vB. Real sizes vary slightly with signature length and with mixed output types.
Block height lookup
Enter any block height to see its subsidy era and how far it is from the next halving and difficulty adjustment.
Rules used: the subsidy started at 50 BTC and halves every 210,000 blocks; difficulty adjusts every 2,016 blocks. Time estimates assume the 10-minute target average — real blocks arrive faster or slower. "Issued" is the theoretical subsidy total; a few coinbase outputs, including the genesis block's, can never be spent.
Address format checker
Paste an address to see its type and network and to verify its checksum. Checking is done on this page only.
A valid checksum means the address was typed correctly. It does not prove that the address belongs to the person you mean to pay — always confirm that through a separate channel.
Notes from the bench
Fees pay for space
Miners charge by virtual size, not by amount. Sending 0.001 BTC can cost the same as sending 10 BTC; spending many small inputs costs more.
Heights are a clock
Block height is Bitcoin's own calendar. Halvings and difficulty adjustments are set in blocks, not dates — dates are only estimates.
Checksums catch typos
Every address format includes a checksum. One wrong character is almost always detected, so a failed check means: stop and copy again.