Bitcoin Fee Estimator

How Bitcoin Transaction Fees Work

Bitcoin transaction fees are payments made to miners who process and confirm transactions on the Bitcoin network. Unlike traditional payment systems with fixed fees, Bitcoin fees are determined by supply and demand for block space.

Every Bitcoin block has a maximum size of about 4 million weight units (roughly 1-1.5 MB of transaction data). When more people want to send transactions than can fit in the next block, fees increase as users compete for limited space.

How Fees Are Calculated

Bitcoin fees are measured in satoshis per virtual byte (sat/vB). The total fee you pay depends on two factors:

• Fee rate (sat/vB): how much you pay per unit of data. Higher rates get confirmed faster.
• Transaction size (vBytes): how much data your transaction uses. More inputs and outputs = larger size.

Total Fee = Fee Rate (sat/vB) x Transaction Size (vBytes)

A typical transaction with 1 input and 2 outputs is about 140 vBytes. At 10 sat/vB, that costs 1,400 sats (about $1.40 at $100k BTC).

Why Fees Vary So Much

Bitcoin fees can range from under 1 sat/vB during quiet periods to over 500 sat/vB during extreme congestion. Several factors affect fee levels:

• Network activity: more transactions competing for space drives fees higher
• Time of day: fees often drop during nighttime hours (UTC) when fewer people are transacting
• Market volatility: price swings cause trading activity spikes
• Ordinals/Inscriptions: NFT-like assets on Bitcoin can consume significant block space
• Exchange movements: large exchanges consolidating UTXOs can temporarily spike fees

Understanding the Mempool

The mempool (memory pool) is where unconfirmed transactions wait before being included in a block. Think of it as a waiting room: transactions with higher fees get processed first.

When the mempool is nearly empty, even low-fee transactions confirm quickly. When it is congested with thousands of transactions, you need higher fees to get priority. Our congestion indicator shows the current mempool state.

Frequently Asked Questions

What is sat/vB?

Sat/vB stands for satoshis per virtual byte. It is the unit used to measure Bitcoin transaction fees. One satoshi is 0.00000001 BTC. Virtual bytes (vBytes) measure transaction size, accounting for SegWit data discounts.

Can I speed up a stuck transaction?

Yes, through two methods: RBF (Replace-By-Fee) lets you rebroadcast with a higher fee if your wallet supports it. CPFP (Child-Pays-For-Parent) creates a new transaction spending the unconfirmed output with a high fee, incentivizing miners to confirm both.

What happens if I set the fee too low?

Your transaction will wait in the mempool until fees drop or eventually be dropped after about two weeks. Most wallets let you increase the fee (RBF) if this happens. Never set fees below the minimum relay fee (usually 1 sat/vB).

When are fees lowest?

Fees tend to be lowest on weekends and during night hours (UTC). Monitoring fee trends and timing non-urgent transactions for quiet periods can save money. Some wallets offer fee scheduling features.

How do Lightning Network fees compare?

Lightning Network fees are typically under 1 satoshi for most payments, regardless of amount. For small or frequent transactions, Lightning is dramatically cheaper than on-chain Bitcoin transactions.