Mempool Fee Estimator
How This Works
Based on Bitcoin network data from the last 3 years, this calculator estimates the optimal fee rate (satoshis per virtual byte) based on current mempool congestion and your target confirmation time.
When you send a Bitcoin transaction and it takes hours-or even days-to confirm, it’s not because the network is broken. It’s because the mempool is full.
What Is the Mempool?
The mempool, short for memory pool, is where unconfirmed transactions wait to be picked up by miners and added to the next block. Think of it like a waiting room at a busy airport: everyone has a ticket (a transaction), but only a limited number of planes (blocks) can take off every 10 minutes. If too many people show up at once, the line gets long. That’s mempool congestion. Every full node on the Bitcoin network keeps its own mempool. There’s no single global mempool. That means if you check your transaction on mempool.space and it shows 80,000 transactions waiting, another node might show 75,000. Why? Because each node has its own rules for what it accepts and how long it holds onto transactions. Bitcoin Core, the most widely used software, sets a default mempool size limit of 300 MB. But that’s not 300 MB of raw transaction data. It includes metadata, indexes, and pointers-so the actual number of transactions stored is less than you’d think. A 300 MB mempool can hold around 150,000 to 200,000 transactions, depending on their size. Once it hits that limit, the node starts kicking out the cheapest transactions first to make room.How Mempool Congestion Works
Congestion happens when more transactions are sent than can fit in the next few blocks. Each block on Bitcoin is limited to about 4 MB (or 1 MB of legacy data, but up to 4 MB with SegWit). At 10-minute intervals, that’s roughly 1,800 to 2,500 transactions per block, depending on complexity. When demand spikes-like during a major NFT drop, a crypto price surge, or a big exchange withdrawal event-transactions flood in faster than blocks can be mined. The mempool grows. And as it grows, fees climb. Miners don’t care about fairness. They care about profit. So they pick transactions with the highest fee rates-measured in satoshis per virtual byte (sat/vB). If you send a transaction with 5 sat/vB, and the mempool is full, yours might sit there for hours. Someone else paying 150 sat/vB? Their transaction gets confirmed in minutes. Blockchain.com’s data shows that when the mempool exceeds 100,000 transactions, confirmation times jump to over 30 minutes. At 150,000+, it’s common to wait 4-12 hours. And if you’re paying only the minimum relay fee of 1 sat/vB? You could be waiting 72+ hours, as seen during the April 2023 congestion spike.
Why Mempool Size Matters
Mempool size isn’t just a number-it’s a leading indicator. It tells you what’s coming before fees spike. If you see the mempool growing steadily over 15-30 minutes, you know fees are about to rise. Waiting until your transaction is stuck is too late. Here’s what different mempool sizes mean in practice:- Under 20,000 transactions: Low congestion. Fees around 5-10 sat/vB. Confirmed in 1-2 blocks.
- 20,000-50,000 transactions: Moderate congestion. Fees 15-30 sat/vB. Confirmed within 1-2 hours.
- 50,000-100,000 transactions: High congestion. Fees 40-80 sat/vB. Wait 2-6 hours.
- Over 100,000 transactions: Severe congestion. Fees 100-200+ sat/vB. Wait 6-24+ hours.
How to Handle Congestion
You don’t have to pay whatever the market demands. Here’s how to navigate it:- Check mempool.space before sending. Look at the current mempool count and the fee estimator. It shows you what fee gets you confirmation in 1, 5, or 60 minutes.
- Use SegWit or Taproot addresses. These reduce transaction size by 20-40%, meaning you pay less in fees for the same transaction. A typical SegWit transaction is 140 vbytes; a legacy one is 225 vbytes. That’s 38% less fee.
- Batch your transactions. If you’re sending Bitcoin to multiple people, combine them into one transaction. Blockstream’s data shows batching cuts total transaction count by 30-50%, saving you money and reducing network load.
- Use Replace-by-Fee (RBF). If your transaction is stuck, you can bump the fee. Most wallets support this. You’re not canceling-it’s just upgrading your priority.
- Child-Pays-for-Parent (CPFP). If you sent a low-fee transaction to someone, and they send a new transaction spending that output with a high fee, miners will prioritize the whole chain. Useful for merchants or wallets stuck in congestion.
maxmempool from 300 MB to 500 MB to hold more transactions. But that uses more RAM. Lowering minrelaytxfee below 1 sat/vB lets you accept cheaper transactions-but you might get flooded with spam.
How Other Blockchains Handle It
Bitcoin’s mempool is fee-driven. Ethereum is different. Since EIP-1559, it uses a base fee that burns with each block and a tip for miners. The base fee adjusts dynamically based on block usage. If blocks are over 50% full, the base fee goes up. If under, it drops. That makes fees more predictable, but doesn’t eliminate congestion. Solana takes another route. It doesn’t use a mempool like Bitcoin. Transactions are processed in parallel by validators, and the network prioritizes speed over decentralization. That’s why Solana can handle thousands of transactions per second-but it’s also why it crashes when overloaded. Layer-2 solutions like the Lightning Network are the real answer to Bitcoin’s mempool problem. During the 2022-2023 congestion spikes, Lightning Network capacity grew 230%. Now, over 40% of Bitcoin’s value transfers happen off-chain, according to Arcane Research. That’s not a workaround-it’s the future.What’s Next for Mempools?
Bitcoin Core 24.0 (released in early 2023) improved how mempools handle eviction during congestion. Version 25.0, coming in late 2024, will add smarter resource management to prevent nodes from crashing under pressure. Taproot adoption is rising. Since November 2021, over 70% of new Bitcoin transactions use Taproot. These transactions are smaller and more efficient, reducing average size by 15-25%. That means more transactions fit in each block-slowing mempool growth without needing a hard fork. Tools like mempool.space are adding predictive models. By analyzing historical congestion patterns, they’ll soon be able to forecast fee spikes hours in advance. That’s huge for exchanges, wallets, and users who need reliable timing. The bottom line? Mempool congestion isn’t a bug-it’s a feature. It’s how Bitcoin ensures security and fair resource allocation. High fees aren’t a failure. They’re the market telling you: “This network is in demand.” But that doesn’t mean you have to pay more than you need to. With the right tools and timing, you can send your Bitcoin quickly, cheaply, and without stress.What is a normal mempool size for Bitcoin?
A normal mempool size ranges from 15,000 to 40,000 transactions during low-traffic periods. During average usage, it sits between 40,000 and 60,000. Anything above 100,000 signals high congestion and likely delays.
Why do some transactions take days to confirm?
Transactions with fees below the network’s minimum relay rate (1 sat/vB) get pushed to the back of the queue. During congestion, nodes evict low-fee transactions first. If your fee is too low and you don’t bump it, your transaction can sit for days-sometimes over a week-before being dropped.
Can I speed up a stuck transaction without paying more?
Not directly. But if you control the receiving wallet (like in a CPFP scenario), you can create a new transaction spending the stuck output with a higher fee. Miners will then prioritize the whole chain. This works best if the original transaction used RBF or if the recipient cooperates.
Does mempool congestion affect altcoins too?
Yes, but less severely. Most altcoins have smaller networks and faster block times, so congestion clears quicker. Ethereum uses EIP-1559 to smooth fees. Litecoin and Dogecoin have larger blocks than Bitcoin, so they handle spikes better. But any blockchain with a mempool and block limits can experience congestion.
Is a large mempool a sign Bitcoin is failing?
No. A large mempool means Bitcoin is in high demand. It’s proof the network is being used. The fee market ensures security-miners are paid to verify transactions, and higher fees make attacks more expensive. Congestion isn’t a flaw; it’s a signal of success. The real issue is when users don’t know how to respond to it.
How often does Bitcoin’s mempool get this full?
It happens several times a year, usually during major events: Bitcoin ETF approvals, large exchange withdrawals, NFT launches, or sudden price surges. The biggest spikes were in 2017, 2021, and early 2023. Since 2022, congestion has become more predictable due to better tools and increased use of layer-2 solutions.
sandeep honey
November 14, 2025 AT 16:11Bro this is the most accurate breakdown of mempool dynamics I’ve seen in months. I’ve been watching mempool.space daily since last year and the fee tiers they listed? Spot on. Just sent a transaction at 45 sat/vB during a 65k mempool spike - confirmed in 2 hours. No drama. No panic. Just math.
Mandy Hunt
November 16, 2025 AT 06:28they dont want you to know this but the mempool is a government tool to track your bitcoin movements and charge you extra for using the people's network
anthony silva
November 17, 2025 AT 06:07so let me get this straight… we’re all paying more so miners can buy more yachts? brilliant economic model. i’m sure the 1 sat/vb guy is just chilling in his basement waiting for his transaction to confirm in 2025
David Cameron
November 19, 2025 AT 02:13the mempool isn’t a problem. it’s a mirror. it reflects how much we value freedom versus convenience. if you want instant, cheap, and easy - go use a bank. if you want sovereignty, you pay the price. the real question isn’t how to avoid fees… it’s whether you’re willing to accept that freedom costs something
Sara Lindsey
November 19, 2025 AT 06:15YES YES YES this is why we need to stop panicking and start strategizing!!! use taproot use batching use rbf you got this!! your bitcoin journey is not defined by mempool stress it’s defined by how smart you play the game!!
alex piner
November 21, 2025 AT 01:54man i used to just send btc and hope for the best now i check mempool.space like it’s the weather app. life changed. also segwit is a game changer honestly i dont know why everyone still uses legacy
Gavin Jones
November 21, 2025 AT 11:59One must acknowledge the elegance of this fee-based congestion mechanism. It is not merely a technical constraint, but a sophisticated economic equilibrium. The mempool functions as a decentralized auction - a testament to the resilience of voluntary coordination in the absence of central authority. Truly, Bitcoin is not just currency - it is a social contract encoded in code.
Mauricio Picirillo
November 22, 2025 AT 09:32big thanks for laying this out so clear. i was so confused before but now i get why my tx took 8 hours. gonna start batching from now on. also taproot is magic lol
Liz Watson
November 22, 2025 AT 23:50Oh wow, so you’re telling me… the same people who told us ‘Bitcoin is digital gold’ are now charging $20 to send $5? How poetic. I guess gold doesn’t have a waiting room
Rachel Anderson
November 23, 2025 AT 07:59my heart literally stopped when i saw 120k in the mempool last week… i thought my entire life’s savings were gone forever… i cried… i screamed… i checked mempool.space again… and then i remembered… i had rbf… i bumped it… and then… i felt… peace
Hamish Britton
November 25, 2025 AT 06:28the lightning network is the real hero here. no one talks about it enough. i sent 17 microtransactions yesterday for coffee and tips - zero fees, instant. bitcoin on chain? for big stuff only. keep it simple
Robert Astel
November 26, 2025 AT 17:14you know what the mempool is really? its like the collective unconscious of the internet trying to decide who gets to be heard. every satoshi is a thought and every block is a moment of clarity. and when the mempool gets full its not just transactions its the weight of human desire pressing against the limits of time and space and the blockchain is the only thing holding it all together like a fragile dream
Andrew Parker
November 27, 2025 AT 05:16the mempool is a trap… designed by the elite to make us feel powerless… they want us to pay more… they want us to rely on layer 2… they want us to forget that bitcoin was meant to be free… i know what they’re doing… i see the patterns… the 1 sat/vb transactions… they’re the ones they want to erase… they’re the ones who still believe in the dream
Kevin Hayes
November 27, 2025 AT 06:19The assertion that mempool congestion is a feature rather than a bug is fundamentally sound. It enforces scarcity, aligns incentives, and preserves decentralization. Any attempt to circumvent this mechanism through artificial fee suppression undermines Bitcoin’s core value proposition. The market determines value - not developers, not regulators, not wishful thinking.
Katherine Wagner
November 29, 2025 AT 06:12why do people even care about mempool size? it’s just a number… and who even uses sat/vb anymore? i just pick 100 and go… why complicate things
ratheesh chandran
November 29, 2025 AT 11:41you think this is bad? wait till the chinese government launches their own blockchain and floods the mempool with fake txs… then youll see real congestion… they already know how to break bitcoin… they just waiting for the right moment
Hannah Kleyn
November 30, 2025 AT 09:45i used to think mempool congestion was just a technical thing… but now i see it as this weird social phenomenon. people are literally bidding for space in a global ledger… like an auction for digital real estate. it’s beautiful in a dystopian way. i sit there watching the numbers climb and i just… wonder. who’s sending all this? what are they buying? who’s waiting? it’s like watching a silent crowd holding their breath
gary buena
December 1, 2025 AT 22:17the fact that you can still send 1 sat/vb tx and it might confirm in 72 hours is kinda beautiful… its like the network says ‘i see you, i remember you, i’ll get to you when i can’… reminds me of how my grandma used to say ‘i’ll call you when i get a chance’… and she always did
Vanshika Bahiya
December 2, 2025 AT 01:29for beginners: if you’re sending to an exchange or wallet you don’t control, always use RBF. if you’re sending to yourself or someone who can help, use CPFP. and always, always check mempool.space before hitting send. this saved me over $200 in fees last month. you got this 💪