What is Bitcoin's security budget after the 2028 halving?
About 0.41% of market capitalisation a year after the ~April 2028 halving, then 0.21% after ~2032 and 0.11% after ~2036, from today’s 0.82% (as of 2026-09-07). No price assumption enters that calculation: price is in the numerator and the denominator and cancels. It is the halving schedule and nothing else.
Why price does not matter here
Today’s 0.82% splits into a subsidy component, which halves on schedule, and a fee component (0.64% of revenue), which does not. Halve the first, hold the second, and the ratio lands at 0.41%. That is below the 0.5% bottom of Lyn Alden’s published band and below any floor anyone has published.
It was called in 2020
Hasu ran this arithmetic on stage in June 2020, when the ratio was just under 2%: “in four years it could be below 1%… in eight years it will be below half a percent.” Eight years from that talk is 2028, and 0.41% is where this page’s figures land. His own answer was that Bitcoin must grow a fee market. Keep going and the ratio reaches 0.21% after ~2032, then 0.11% — the two levels James McAvity named as the point where “it’s just a different system. It’s a different protocol.”
What it would take to hold 1%
Hold the best fee month in Bitcoin’s history flat forever and the post-2028 gap is still about $4.71B a year. Fees would have to reach a level Bitcoin has never recorded. That is why the question how big is the gap is a dial, not a threshold: every dollar of external funding fills part of it, and after 2028 there is more of it to fill.