51% Attack Cost Calculator
Calculate the estimated cost of a 51% attack on a cryptocurrency based on its hashrate and market cap. Understand whether an attack would be profitable for an attacker.
Results will appear here after calculation
Imagine you own a small digital currency worth $500,000. It’s traded on a few niche exchanges, mined by a handful of people, and has no big-name backers. Now imagine someone pays $20,000 for a few days of rented mining power-and suddenly, they can erase your transactions, steal your coins, and make it look like they never happened. This isn’t science fiction. It’s what happens in a 51% attack.
What Exactly Is a 51% Attack?
A 51% attack happens when one person or group controls more than half of a blockchain’s total mining power. In proof-of-work systems like Bitcoin or Ethereum Classic, miners compete to solve math problems and add new blocks. Whoever controls the majority of this computing power gets to decide which transactions go through-and which ones get erased. You might think, “That’s impossible.” But it’s not. For Bitcoin, you’d need billions of dollars in hardware and electricity. For a small crypto with a daily hashrate of just 100 TH/s? You could rent the power for less than the cost of a used car. The attacker doesn’t need to hack wallets or steal private keys. They don’t create new coins out of thin air. What they do is far more dangerous: they rewrite history. They can reverse your payment to an exchange, send the same coins to another address, and then claim they never sent the first one. That’s called double-spending. And once the attack is done, the damage is permanent.Why Small Cryptocurrencies Are Sitting Ducks
Bitcoin has over 700 exahashes of mining power. That’s 700 million terahashes. It’s like trying to take over a stadium full of armed guards. Now consider Feathercoin, which had less than 100 TH/s in 2018. That’s like trying to take over a single security guard. The math doesn’t lie. Small cryptocurrencies have three fatal flaws:- Low hashrate: Fewer miners mean less total computing power. That makes it cheaper to overpower them.
- Centralized mining pools: Often, 3-4 pools control 80% of the network. Take over one, and you’re halfway there.
- Low market cap: If the total value of the coin is under $10 million, a $50,000 attack can be profitable. You steal $100,000 in coins, sell them, and walk away with a 100% profit.
How Attackers Do It (And How Cheap It Is)
There are three ways to pull off a 51% attack:- Rent mining power: Services like NiceHash let you rent hashpower by the hour. For $15,000, you can rent enough power to take over a top-100 crypto for 24 hours.
- Use cloud mining: Companies like Genesis Mining offer contracts to mine on their hardware. You don’t own gear-you just pay for access.
- Team up with other miners: If you can convince a few mining pools to coordinate, you can hit the 51% threshold without spending a fortune.
What Attackers Can (and Can’t) Do
It’s important to understand the limits:- They CAN: Reverse transactions, block new ones, reorganize the chain, prevent others from mining.
- They CANNOT: Steal coins from wallets, change supply limits, create new coins, alter private keys.
Real-World Damage: Beyond the Money
The financial loss is bad-but the reputational damage is worse. After Bitcoin Gold’s 2018 attack, developers stopped working on it. Investors pulled out. Trading volume dropped 90%. Today, it’s a ghost of its former self. The same thing happened to Krypton and Verge. One attack didn’t just cost them money-it killed their future. Users lost trust. Developers moved on. Exchanges removed listings. And once that trust is gone, no amount of marketing or new features can bring it back.Can These Attacks Be Stopped?
There are fixes-but they come with trade-offs:- Checkpointing: Hardcode trusted blocks at certain heights. Prevents deep reorgs. But it centralizes control-someone has to decide which blocks are “trusted.”
- Longer confirmations: Require 10 or 20 confirmations instead of 6. Slows down transactions but makes attacks harder to pull off.
- Diverse mining pools: Encourage miners to spread across many pools, not just 2-3. Hard to enforce.
- Community monitoring: If users spot unusual reorgs, they can alert exchanges and halt withdrawals. But most users don’t know how to check.
Who’s at Risk Right Now?
As of late 2025, over 200 cryptocurrencies have market caps under $10 million. Most of them have less than 1 TH/s of mining power. That’s less than what a single high-end ASIC miner can produce. If you’re holding any of these, you’re playing Russian roulette:- Cryptocurrencies with names you’ve never heard of
- Coins that don’t list their hashrate publicly
- Projects with no active development in 6+ months
- Coins traded only on small, unknown exchanges
What Should You Do?
If you’re a holder:- Don’t hold small cryptos long-term. Treat them like speculative bets, not investments.
- Withdraw coins to your own wallet immediately after a trade. Don’t leave them on exchanges.
- Wait for at least 10 confirmations before considering a transaction final.
- Check the coin’s hashrate on sites like Crypto51.app. If it’s under 100 TH/s, walk away.
- Don’t build on a chain with low hashrate. It’s a ticking bomb.
- Push for hybrid consensus models (proof-of-stake, proof-of-authority) if possible.
- Support projects that publish real-time mining data and have transparent pool distribution.
The Future Is Bleak-Unless You’re Bitcoin or Ethereum
The trend is clear: as cloud mining gets cheaper and attack tools become more accessible, small cryptos will keep getting wiped out. There are already underground services offering “51% attack packages” for rent. You pick the coin, pay in Bitcoin, and get a script that runs the attack. Only networks with massive, distributed mining power-Bitcoin, Ethereum, Litecoin-have real protection. Everyone else is just waiting for their turn. The lesson isn’t that blockchain is broken. It’s that decentralization only works when it’s expensive to break. When the cost of attack drops below the value of the target, the system fails. And for most small cryptocurrencies, that point was reached years ago.Frequently Asked Questions
Can a 51% attack steal my crypto from my wallet?
No. A 51% attack can’t access your private keys or take coins directly from your wallet. It can only reverse transactions that were already confirmed on the blockchain. If your coins are in your own wallet and you never sent them out, they’re safe. The danger is when you send coins to an exchange or another user-those transactions can be reversed.
How much does a 51% attack cost?
It depends on the coin. For Bitcoin, it would cost billions. For a small crypto under $10 million market cap, it can cost as little as $5,000 to $50,000 for a few hours of rented mining power. Services like NiceHash let you rent hashpower for as little as $0.01 per GH/s per hour. If a coin has 100 TH/s total, you’d need to rent 51 TH/s-around $500/hour. A 24-hour attack? Under $12,000.
Are there any small cryptocurrencies that are safe from 51% attacks?
Very few. If a coin has a market cap under $10 million and uses proof-of-work, it’s almost certainly vulnerable. Some coins use proof-of-stake (like Solana or Cardano), which makes 51% attacks nearly impossible because you’d need to own 51% of all coins-not just mining hardware. But proof-of-stake coins have their own risks. For proof-of-work coins, only those with hashrate over 10,000 TH/s and strong decentralization have any real protection.
Why don’t exchanges just block these attacks?
Exchanges can’t stop the attack itself-they’re not part of the blockchain. But they can delay withdrawals, require more confirmations, or delist coins after an attack. Most exchanges now monitor for unusual reorganizations. If a coin has a deep chain reorg (more than 10 blocks), they’ll freeze deposits and withdrawals until the situation is resolved. That’s why many small cryptos get delisted after one attack-they become too risky to handle.
Is proof-of-stake safer than proof-of-work?
Yes, for this specific threat. In proof-of-stake, you need to own 51% of all coins to attack the network-not just mining equipment. That’s astronomically expensive. For example, to attack Ethereum, you’d need to buy over $50 billion worth of ETH. That’s not just impractical-it would crash the market before you could even start. So proof-of-stake coins are far less vulnerable to 51% attacks. But they have other risks, like validator centralization or slashing penalties.
Comments
13 Comments
Adam Bosworth
Bro this is why I never touch anything below BTC or ETH. I saw a guy lose $40k on some coin called 'DogeCoin2.0' because of a 51% attack. He thought it was 'undervalued'. Nah. It was a trap with a countdown timer.
Renelle Wilson
It's important to recognize that the underlying principle of blockchain-decentralized trust-is being undermined not by technology, but by economic incentives. When the cost of disruption falls below the value of the target, rational actors will exploit it. This isn't a flaw in cryptography; it's a failure of market design. We must ask: Is decentralization sustainable if it's cheaper to break than to build?
Elizabeth Miranda
I’ve held a few small cap coins just to learn. Never kept them longer than a week. The moment I saw the hashrate on Crypto51.app was lower than my laptop’s GPU output, I pulled out. No drama. Just math.
Chloe Hayslett
So let me get this straight-people are still putting money into coins that cost less to attack than a nice dinner? What planet are you living on? This isn't investing. It's gambling with a side of delusion.
Jerry Perisho
The real issue isn't the attack-it's the lack of transparency. Most small coins don't even publish their hashrate. If you can't see the numbers, you're not investing. You're guessing. And guesses get erased.
Manish Yadav
This is why we need to stop all this crypto nonsense. It's all fake. People lose money. Governments should ban it. Why let people be fooled like this?
Chris Jenny
I knew it... I KNEW IT!!! The deep state is using NiceHash to buy hashpower and collapse small chains to push people into CBDCs!!! They control the cloud miners, the exchanges, the developers-EVERYTHING!!! Look at the timing of the attacks... always right after a major news cycle!!! They want you to trust only the dollar!!! I’ve seen the patterns!!!
ronald dayrit
The tragedy here isn't the vulnerability of the blockchain-it's the human tendency to confuse novelty with value. We are drawn to the idea of decentralization as a moral imperative, yet we willingly entrust our capital to systems that are structurally, economically, and psychologically fragile. The blockchain doesn't fail us; we fail the blockchain by expecting it to be more than a tool, and less than a gamble dressed in ideology.
Uzoma Jenfrancis
America thinks it owns crypto because it has the most ASICs. But Africa has the people. The real power isn't in machines-it's in the minds that use them. You can rent hashpower. You can't rent patience. Or wisdom.
Vincent Cameron
If you believe in decentralization, then you must accept that some chains will die. Death is part of evolution. The question isn't whether small coins will be attacked-it's whether we, as a community, will mourn them or learn from them. The blockchain is not a monument. It's a process.
Mairead Stiùbhart
Oh sweetie, you just spent 10 minutes explaining why your $500 investment is basically a candle in a hurricane. Congrats. Now go put that money in a savings account and call it a day.
Noriko Robinson
I read this whole thing and just felt so sad. So many people pour their hearts into these projects, thinking they're building the future, and then one day, someone rents a few GPUs and wipes it all out. It's not just money-it's dreams. We need better systems, not just warnings.
Thomas Downey
The fact that this article even needs to be written speaks to the profound intellectual decay of the modern investor. To treat a blockchain with a market cap under $10 million as anything other than a speculative fiction is not merely unwise-it is a moral failure of discernment. One does not build a cathedral with matchsticks and then complain when the wind blows it away.
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