Crypto Newbie / Simulators / Proof of Work
Proof-of-Work Simulator — Mining Math, Concentration, 51% Attack
Bitcoin and most layer-1s before 2022 used Proof-of-Work: miners race to find a hash below the difficulty target, and whoever finds one first wins the block reward. This simulator runs the same probability math — set hashrate per miner, simulate hundreds of blocks, and watch how concentration risk + electricity cost actually shape mining economics. No GPUs harmed.
Network configuration
| Miner | Hashrate (TH/s) | W per TH/s | Electricity ($/kWh) |
|---|---|---|---|
| Big farm | |||
| Mid farm | |||
| Home rig |
Per-miner results
| Miner | Expected % | Actual % | Daily revenue | Daily cost | Daily profit |
|---|---|---|---|---|---|
| Big farm | 58.8% | 57.0% | $25.15M | $2 | $25.15M |
| Mid farm | 35.3% | 37.0% | $15.09M | $2 | $15.09M |
| Home rig | 5.9% | 6.0% | $2.51M | $1 | $2.51M |
51% attack cost
$0/h
Hourly cost for an attacker to rent enough hashrate to exceed the honest network. Estimated using the network's average power efficiency + electricity cost.
Concentration
58.8%
⚠ One miner controls > 50% of hashrate — chain is centralised.
How block-discovery probability works
Every miner is trying random nonces and hashing them. The chance that any given hash lands below the target is the same for every miner per attempt. So the probability of winning the next block is simply your share of total network hashrate. If you contribute 10% of the hashrate, you'll win ~10% of blocks over a long enough window. Short-term it's high variance — a solo miner with 1% hashrate may go weeks between blocks even though their expected block time is ~17 hours.
Difficulty adjustment keeps block time stable
If the network's combined hashrate doubles, blocks would be found twice as fast — every 5 minutes instead of 10. Bitcoin's difficulty adjusts every 2016 blocks (~2 weeks) to retarget the average block time back to 10 minutes. This is what makes PoW supply schedules predictable even when miners come and go. Other PoW chains use shorter retargeting periods; Bitcoin's slow adjustment is deliberate for stability.
The economics: revenue vs electricity
Revenue = expected blocks per day × block reward × coin price. Cost = hashrate × watts per TH × hours × electricity rate. When coin price falls, marginal miners (those paying $0.10+/kWh with older ASICs) go offline — which lowers network hashrate, which triggers a downward difficulty adjustment, which makes remaining miners more profitable. This negative feedback loop is why Bitcoin mining has a floor price determined by the cheapest electricity in the world.
Why 51% attacks are mostly theoretical for Bitcoin
An attacker needs hashrate slightly greater than the honest network — call it 51%. The cost to rent that much hashrate for an hour is roughly the network's hourly electricity bill. For Bitcoin in 2026 that's millions of dollars per hour. For small PoW altcoins it can be under $1000/hour — and small-cap chains have been 51%-attacked many times (Ethereum Classic, Bitcoin Gold, Verge). Use this simulator to see the cost difference for yourself.
Frequently asked questions
+Why does my actual block share not match my expected percentage?
Variance. With only 100 simulated blocks, random outcomes can deviate 5-10% from expected probabilities. Run with 10000 blocks and you'll see actual converges almost perfectly to expected. This is why small miners join mining pools — pools smooth out variance by sharing rewards proportionally to contributed hashrate, even though only one pool member finds each block.
+What's the difference between PoW and PoS?
PoW uses real-world energy (electricity → ASIC compute) as the cost of attempting to produce a block. PoS uses locked-up capital (stake) as the cost. Both create economic friction that secures the chain. PoW's security scales with electricity cost; PoS's security scales with token market cap. Ethereum switched from PoW to PoS in 2022, cutting energy use by ~99.95%.
+Why is electricity cost so important in this simulator?
Mining is a commodity business — the product (BTC) sells at one price worldwide, but production costs (electricity) vary 10× between locations. Miners with $0.04/kWh hydro in Sichuan or Texas are profitable; miners with $0.15/kWh grid power in Europe are typically not. This is why mining operations relocate constantly chasing cheap power.
+What does '51% attack' actually let an attacker do?
Double-spend: confirm a transaction, send the coins to an exchange, sell, then privately mine an alternate chain that doesn't include the deposit. When the alternate chain becomes longer, the network reorganises to it — the deposit transaction disappears, but the exchange already paid out. The attack does NOT let them steal arbitrary coins, mint new coins, or change supply rules. Only reverse their own recent transactions.
+Can a single miner ever own more than 50% on Bitcoin today?
Theoretically yes, practically very hard. Bitcoin's network hashrate is ~700 EH/s in 2026 — replicating that costs ~$30-50 billion in ASIC capex + ongoing power, and any miner approaching 50% would face social/protocol response (community moving to PoS or hard-forking). Concentration risk on Bitcoin today comes from pools (Foundry, Antpool) coordinating multiple smaller miners, not single-entity hashrate ownership.