Bitcoin · live

What would it take to attack Bitcoin today?

A 51% attack means mining faster than everyone else combined, so you can rewrite recent blocks and spend the same coins twice. The costs below are worked out from live network data.

Network hashrate—what an attacker has to beat

Rented hashpower, per hour—at NiceHash’s going rate

Hashpower for rent—of what an attack needs

Miners earn, per hour—block rewards and fees, last 144 blocks

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If you had to own the machines

Rental can’t cover it, so an attacker would have to build a mining operation as big as the rest of the world’s.

Machines—at 200 TH/s each, a current top-end ASIC

Power draw—at 17.5 joules per terahash

Hardware cost—at $15 per TH/s, before buildings and power

The machine figures are estimates from the assumptions under each number. An attacker would also have to buy that many machines without pushing up their price, and find the power to run them.

Hashrate over the past year

Seven-day average. Every rise makes an attack more expensive.

Who mines the blocks

Share of blocks mined in the past week, by pool.

A pool coordinates miners without owning their machines, and miners can leave a pool that misbehaves. The pool does choose which transactions go into blocks, so a few pools acting together could censor transactions or try a short reorganisation. Some smaller pools pass their work to a larger one, which would make the real concentration higher than this chart shows.

Every reachable node

Nodes check every block and reject invalid ones, whoever mined them. Loading…

Each dot is a location with at least one reachable node. Nodes on Tor and I2P have no location, so they aren’t on the map.

Nodes by network

How these numbers are worked out

The hashrate is mempool.space’s estimate from recent blocks. To out-mine the network, an attacker needs at least as much again.

Rent per hour is the network hashrate multiplied by the speed-weighted price of live orders on NiceHash, the largest hashpower marketplace. Prices move quickly, and an attacker buying the whole market would push them up.

Hashpower for rent is what NiceHash buyers are receiving right now, compared with the network’s total. Rental attacks have worked against smaller coins, but for Bitcoin this is a fraction of a percent of what an attack needs.

Miners’ earnings are the block subsidy plus fees over the last 144 blocks (about a day), shown per hour.