What is Bitcoin's security budget?
Bitcoin’s security budget is what miners are paid to secure the chain: the block subsidy plus transaction fees. Over the trailing year to 2026-09-07 that was $14.36B, or about 0.82% of a $1.56T market capitalisation.
The two components
The subsidy is newly issued bitcoin, 3.125 BTC per block today, cut in half roughly every four years until it reaches zero around 2140. Fees are paid by users competing for block space. The subsidy is scheduled and shrinking; fees are market-determined and, at 0.64% of miner revenue over the last 30 days, currently small.
Why it is measured against market capitalisation
Miner revenue is a flow and what it protects is a stock, so the useful form is a ratio: annualised miner revenue divided by market capitalisation. That is 0.82% today. Expressed the other way, $0.0082 of security spending a year backs every dollar of Bitcoin market cap.
Why anyone worries about it
The subsidy is most of it. When the subsidy halves, the budget halves with it unless fees make up the difference. The ratio falls to 0.41% after the ~April 2028 halving, 0.21% after ~2032 and 0.11% after ~2036, and no price assumption enters that calculation, because price appears in both the numerator and the denominator and cancels. See the size of the gap and the 2028 figure.
| Basis | Ratio | Gap / yr | Market cap to cover it |
|---|---|---|---|
| Trailing-year revenue over spot market cap | 0.92% | $1.27B | $24.40B |
| Trailing-year revenue over average market cap | 0.86% | $2.13B | $40.93B |
| Spot run-rate revenue over spot market cap (published) | 0.82% | $2.77B | $53.28B |
Three ways to measure the same ratio, all published. None of the three closes the gap.