ENOctober 6, 2026Mikail Aslan

How to measure an automatic watch's daily rate

A practical way to observe an automatic watch's daily rate, distinguish a pattern from one reading, and know when to consult a professional.

Last fact-checked: October 6, 2026

Measure an automatic watch’s daily rate by recording its offset from the same time reference at the start and end, then dividing the change by the elapsed time in days. This gives the average daily rate; repeated measurements under similar wearing and resting conditions reveal whether a pattern is emerging.

What a daily rate actually records

The displayed offset is the difference between the watch and the reference at one reading: ahead is positive, behind is negative. Daily rate is the change in that offset per day. A watch can therefore still display a time ahead of the reference while having lost time during the measurement. You need both the starting and ending offsets to identify the direction of change.

Mechanical accuracy is influenced by conditions as well as the mechanism. Seiko lists temperature, gravity and resting position, shock, the movement of the wearer's arm and the mainspring's winding state among factors that can affect gain or loss. Its explanation of mechanical accuracy is a useful reason to record conditions instead of treating every figure as a fixed property.

“Daily rate” is simply a practical label for change over about a normal day. The context makes it meaningful. Was the watch worn from morning to evening, left on a desk for much of the day, or put on after it had not been worn for a while? Was it stored the same way overnight? Those details are not a laboratory protocol; they let you compare like with like.

Set up a simple, repeatable log

No specialist timing machine is needed for this first observation. Use one reliable, automatically updated source of time and keep using the same one. Avoid resetting the hands in the middle of a series. If you reset the watch, close that series and begin a fresh one so the numbers remain understandable.

Record	Why it matters
Start time and displayed difference	Establishes the point from which change is read.
Next comparison time	Connects the difference to a defined interval.
How the watch was worn	Separates an ordinary active day from long rest.
Overnight resting position	Gives useful context for a face-up, back-up or side position.
Unusual event	Keeps a knock or possible magnetic exposure separate from guesswork.

Choose an exact starting time you can repeat without effort, read the existing offset against your reference and note it without resetting the hands. For example, record “+4 seconds” at the start, then “+14 seconds” exactly 48 hours later. In this hypothetical example, the daily rate is (+14 − +4) ÷ (48 ÷ 24) = +5 seconds per day. That calculation describes this interval only; it is not a specification, a guarantee or a forecast.

Several comparable days are normally more useful than checking every few minutes. Frequent checks can make ordinary short variation feel dramatic. Fixed morning or evening notes let you see a line rather than a collection of impressions. Afterwards, ask a modest question: did the result move in a similar direction on comparable days, fluctuate without a clear direction, or change suddenly after an identifiable event?

Three figures that should not be mixed

The TMI guide for the NH3 series lists a static accuracy range of −20 to +40 seconds per day for the movement under its stated measurement conditions, including full winding and defined positions. The technical guide also describes a short instrument measurement after winding; it is not the same as an all-day wear record. A timing-machine reading is a momentary sample, while your start-offset/end-offset log describes what your finished watch showed over real elapsed hours. Neither figure predicts a particular MedoMods watch.

A trend is different from a single result

A snapshot answers “what is the difference right now?” A trend answers “how did the difference change while the relevant conditions stayed broadly similar?” This distinction is valuable because it stops a single surprising reading from becoming a conclusion about the whole watch.

What you notice	Careful interpretation	Useful response
One result differs from earlier notes	The day or rest period may have been different	Continue the log and note the context
Comparable days move in one direction	A pattern may be developing	Keep the records together
A new pattern begins after a known event	The timing is relevant information	Take the notes to a professional
The display changes much more than usual	The cause cannot be identified remotely	Arrange an assessment rather than experimenting

Do not calculate unequal intervals as though they tell the same story. A half-day comparison and a full-day comparison can both be informative, but label them as such. “Worn today” is also more helpful when paired with a plain description such as a typical workday, a quiet day at home or a long period off the wrist. The aim is not to control your routine. It is to avoid confusing a change of routine with a change in the watch.

Wearing, winding and resting position

Movement of the wrist supplies energy to an automatic watch's mainspring. Seiko says sufficient winding helps mechanical accuracy remain more stable and explains that, as available energy falls, the regulating parts can be more susceptible to outside influences. Its guidance on winding state is written for the manufacturer's own watches, so it is context rather than a universal operating prescription.

For a log, the practical point is modest: include whether the watch had been lying unused before the measurement or had been worn in its usual rhythm. That note cannot diagnose the watch from a distance. It can stop an atypical low-energy period from being mixed silently into a run of normal days.

Resting position can matter too. Seiko explains that gravity affects the mechanism differently when a watch is off the wrist and gives dial-up, back-up and side positions as examples. Its accuracy FAQ supports recording the position you happened to use; it does not make home experimentation a substitute for professional service.

Temperature and impacts deserve the same calm approach. Seiko warns that extreme temperatures and hard shocks can affect accuracy. When an unusual result follows a knock, write down when it happened and seek advice if the change persists. There is no need to open the watch or alter anything inside it to make that record useful.

Magnetism: note the possibility, do not self-treat

Magnetic objects are ordinary surroundings. Seiko names phones, speakers, magnetic closures, hair dryers and electric shavers among possible sources, and says a mechanically driven watch may gain or lose time after magnetic influence. Its magnetism FAQ also says a mechanical watch can remain magnetized after being moved away from the source and recommends professional demagnetization when that is suspected.

In a notebook, “longer proximity to magnetic accessory possible” is enough. It is a neutral fact, not a diagnosis. Do not test the watch with magnets or attempt a home remedy: neither establishes the cause reliably. A qualified professional can assess the complete watch and decide what examination is appropriate.

When to consult a professional

A log is not a repair assessment. It makes an appointment more productive when the result is clearly and persistently different from your previous pattern, follows a hard impact, or coincides with a plausible magnetic exposure. Bring the sequence of readings, your usual wear pattern and the date of any notable event. A short, factual record is better evidence than a remembered estimate.

The professional can determine the appropriate next step in person. This article deliberately avoids advice on self-opening, regulation or demagnetization. An uncertain intervention is not a substitute for an informed assessment of a finished watch.

Keep accuracy separate from choosing a watch

When comparing a mechanical watch, treat rate observation and design choice as separate questions. The DATE MOD collection and CLASSIC MOD collection are places to compare dial, bracelet and currently offered variants at your own pace. Neither page can predict the individual daily rate of a particular watch.

For published movement context, read NH35 vs. NH36; for crystal choices, see sapphire versus mineral crystal. The site's watch-care page is the better destination for normal cleaning and care. This guide stays focused on making an accuracy observation clear enough to use.

Frequently asked questions

How do I measure an automatic watch's daily rate?

Record the starting and ending offsets from the same time reference. Divide their change by the elapsed time in days and repeat under similar conditions.