Work out ntp offset instantly with clear inputs, formula shown and shareable results.
NTP derives offset from four timestamps as ((T2 - T1) + (T3 - T4)) / 2 and round-trip delay as (T4 - T1) - (T3 - T2). The formula assumes the path is symmetric; any asymmetry translates directly into offset error bounded by half the round-trip delay, which is why low and stable latency matters more than raw accuracy of the reference clock.
NTP offset and delay
offset = ((T2 - T1) + (T3 - T4)) / 2; delay = (T4 - T1) - (T3 - T2); worst-case error = delay / 2
The calculation splits round-trip delay equally between the two directions. If one direction is slower, that difference appears as apparent clock offset.
By default 1000 seconds, above which ntpd exits rather than stepping the clock. Offsets above 128 ms are stepped rather than slewed.