How BackPoW calculates solo mining odds

Most mining calculators tell you ‘coins per day’, as if mining paid out on a schedule. It doesn’t. Block discovery is a memoryless random process, and treating it as linear is the single most common mistake in solo mining. This page documents exactly what BackPoW computes, so you can check it, argue with it, or reimplement it yourself.

1. Why the odds are not linear

Every hash your machine computes is an independent trial with a tiny, constant probability of success. The network has no memory of your previous attempts: having mined for three years without a block does not make you ‘due’ for one. Formally, block discovery is a Poisson process, and the waiting time between blocks follows an exponential distribution.

The practical consequence is counter-intuitive, and it is the reason this site exists: if your rig has a 1-in-2 chance of finding a block in a year, it does not have a 1-in-1 chance in two years. It has about 75%.

2. Expected time to a block

The mean time T between blocks for your hashrate is T = network_hashrate ÷ your_hashrate × block_time. BackPoW uses this form because it holds on every chain regardless of how that chain defines difficulty. On Bitcoin-style chains it is equivalent to the familiar T = (D × 2³²) ÷ H, since network_hashrate = D × 2³² ÷ block_time.

3. Probability over a period

The chance of finding at least one block within a window t is P(X ≥ 1) = 1 − e^−t/T. This is what BackPoW reports for a day, a month and a year — not a linear fraction. For a target number of blocks k, the same Poisson model gives P(X ≥ k), which drives the multi-block scenarios on the calculator.

4. What the numbers are worth

A block is valued in native units and USD from live market pricing. Electricity uses a default of $0.069/kWh, adjustable on every calculator. BackPoW also publishes a Cost of Production (CoP) per coin — the implied cost to mine one unit — which is what makes it possible to say whether a coin is currently being mined at a loss.

5. Data sources and freshness

Network difficulty, hashrate, block time and block reward come from live network and pool data, refreshed daily. Hardware specifications (hashrate, power draw) and market prices are aggregated across multiple vendors. Every figure on the site is derived from these inputs — nothing is hand-entered per page.

6. Honest limits

Difficulty changes over time; the odds shown assume the current difficulty holds.
Expected value is not a forecast. Over any single year the most likely outcome for a small rig is zero blocks, even when the expected reward looks favourable.
Pool luck, orphan/uncle rates and pool fees are not modelled in the base odds.
Prices are volatile; a block’s USD value is a snapshot, not a promise.

Use these numbers

All of this is available as a free public JSON API. Citation with a link back is all we ask.