Fault-Tolerant Resource Estimator

How many physical qubits, and how long, would an algorithm need under surface-code error correction? It is the question most algorithm papers end on, and nobody can answer it by running anything — the machine does not exist yet. So it is answered by a model: surface-code logical error scaling, lattice-surgery timing and 15-to-1 magic-state distillation. Read every result as a power of ten.