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Transactions: the waiting room, the fee, and the stamp of approval
When you send a transaction, it goes into the mempool — a waiting area of unconfirmed transactions. Miners/validators pick transactions from the mempool, usually preferring those paying higher fees (called gas on Ethereum). Once included in a block, your transaction has 1 confirmation; each subsequent block adds another. More confirmations = more certainty the transaction is final.
From wallet to three confirmations
Confirmation times & expectations
How long a transaction takes to confirm depends on the chain’s block time and how much fee you pay relative to others. Concrete reference numbers:
| Chain | Block time | Typical 1st conf. | Confirmations for “final” |
|---|---|---|---|
| Bitcoin | ~10 min | ~10 min (1 block) | 6 (~1 hour); exchanges often require more |
| Ethereum | ~12 s | ~12 s (1 slot) | ~64 slots, two epochs (~13 min); exchanges set their own counts |
| Ethereum L2s (Arbitrum, Base) | <1 s (Arbitrum); 2 s (Base) | sub-second (L2) | 1 on L2; true finality tracks Ethereum (tens of minutes, once its batch is posted and finalized) |
| Solana | ~0.4 s | sub-second | ~32 (optimistic slots) |
What affects speed: fee level (higher = miners/validators prefer you), network congestion (more demand = higher bar to be included), and mempool backlog. If your fee is too low, your transaction can sit unconfirmed for hours or be dropped. Two recovery tools: RBF (replace-by-fee — resubmit paying more) and CPFP (spend the unconfirmed output with a high fee to incentivize confirming both).
Expectations: on L2s and Solana, expect seconds. On Ethereum, expect seconds for inclusion and about 13 minutes for finality. On Bitcoin, expect ~10 minutes for one confirmation and ~1 hour for high-confidence finality. Always check a block explorer if a transaction seems stuck before resubmitting.
Confirmation time estimator
Pick a chain and fee tier to see the block time, estimated wait to the first confirmation, and the recommended confirmation count for “final.” Numbers are illustrative estimates — real waits vary with live congestion.
- Block time
- ~10 minutes
- Est. wait to 1st confirmation
- ~1 block (~10 min)
- Recommended confirmations for final
- 6
- Approx. time to final
- ~1.0 hours
Tip: if a transaction is stuck (low fee, congested mempool), use (replace-by-fee) or to push it through — both are covered in the glossary.
Two ways to keep the books: UTXO vs. account
| Model | Used by | Mental model |
|---|---|---|
| UTXO | Bitcoin | Balances are sets of spendable "coins" (outputs) |
| Account | Ethereum | Balances are stored per account, like a bank |
Coins or balances