To capture a signal faithfully, sample above 2× its highest frequency — in practice 5–10×.
The Nyquist–Shannon limit is a hard floor, not a target: real systems need margin for filters, noise and phase.
Nyquist assumes you have band-limited the signal first. Sample a signal containing anything above half your rate and that content does not disappear — it folds down and lands on top of real data, indistinguishable afterwards. The anti-alias filter is the part of the rule people skip.
Estimate with the rule, then check it against the calculator that models it properly.
Open Sampling & Aliasing →