Updated October 2026
Once this tool gives you a rate reading in seconds/day, the natural next question is: is that number actually good? The honest answer depends heavily on what kind of watch you're testing — a "good" number for a 1960s pocket watch and a "good" number for a current chronometer-certified watch are very different.
Rate is how many seconds a watch runs fast (positive) or slow (negative) per 24 hours, derived by comparing the watch's actual measured average tick interval to the theoretical interval implied by its stated beat rate — the full math is on how this works. A rate of 0 s/day would mean perfect timekeeping; essentially no mechanical watch holds exactly 0 across all conditions, so the question is really "how close, and is that typical for this kind of watch."
The results panel flags your measured rate into one of three bands: under 10 seconds/day absolute deviation is flagged "Good," 10-30 s/day is "Noticeable," and beyond 30 s/day is "Large deviation." These thresholds are a reasonable general-purpose cutoff, but "good" genuinely depends on tier — read on for the context behind each band.
A COSC-certified Swiss chronometer movement is tested and required to run within roughly -4 to +6 seconds/day across a battery of positions and temperatures — a tight tolerance that sits well inside this tool's "Good" band. If you're testing a certified chronometer and seeing anything in the "Noticeable" or "Large deviation" range, that's worth taking seriously — either the measurement conditions are affecting the reading (see getting an accurate reading) or the watch may genuinely need attention.
Most non-chronometer-certified modern mechanical movements (common commercial calibers and many in-house movements without formal certification) are generally expected to run somewhere in the ±10 to ±20 seconds/day range fresh from the factory or after a proper service — comfortably in or near this tool's "Good" band, sometimes nudging into "Noticeable." This is a completely normal range and not a sign of a problem by itself.
Older movements, and any mechanical watch that hasn't been serviced in many years, routinely drift wider — ±30 seconds/day or more isn't unusual and doesn't automatically mean something is broken; lubricant aging and general wear naturally widen rate tolerance over time. A vintage piece reading "Large deviation" on this tool is common and, by itself, isn't alarming — see vintage watch rate and beat error expectations for a fuller picture of what's normal for older pieces specifically.
Rate genuinely varies by position (dial up vs. crown down, for example — see testing positions) and can drift somewhat over the course of a watch's power reserve. A single 15-second capture is a snapshot, not a certified average across positions and time the way a professional multi-position regulation report would be. Testing in two or three positions and noting the spread gives a much more trustworthy picture than any single number.
A newly serviced or purchased watch landing solidly in "Large deviation" across multiple careful tests (quiet room, full 15-second capture, correct bph selected) is worth having checked by a watchmaker — not because this tool's number is a certified diagnosis, but because it's a reasonable first signal that something may be off with regulation or lubrication. See how to tell if your watch needs service for how to combine rate with beat error and amplitude trend into a fuller picture before deciding.
Is "Good" on this tool the same as chronometer-grade? Not necessarily — "Good" (under 10 s/day) is a reasonable general bar, but true chronometer certification involves multi-position, multi-temperature testing on calibrated equipment that this tool doesn't replicate.
Does rate change with how full the mainspring is wound? Yes, to some degree — many mechanical watches show slightly different rate near full wind versus near the end of their power reserve; a single test captures only the state at that moment.
Is a watch running fast better or worse than running slow? Neither is inherently better — what matters is the magnitude of deviation from zero and whether it's consistent, not the direction.