Reading Watch Accuracy on a Japanese Listing: 日差, Beat Rate (2026)

2026.09.10

Japanese pre-owned watch listings often carry a line most foreign buyers skip: an accuracy reading such as 日差 +3秒（平置き実測）, a beat rate like 振動数 28800, or a timegrapher photo full of numbers. This guide explains how to read the accuracy figures on a Japanese watch listing — 日差 (daily rate), 精度, 振動数 (beat rate), 振り角 (amplitude) and 片振り (beat error) — what counts as normal for each movement type, and why the number in the listing is not the number you will see on your wrist.

It sits alongside our guides to service terms (OH済, 要OH, 研磨) and box and papers (full set vs head only): same job, different line of the listing. Here we read the accuracy line. All figures are stated as of September 2026 with a primary source, because certification tolerances and caliber specs do change.

What “accuracy” means on a Japanese watch listing

日差 (nissa) is the daily rate: how many seconds a mechanical watch gains (+) or loses (−) over 24 hours, measured on a timegrapher. A listing that says 日差 +3秒 means the watch ran three seconds fast per day at the moment it was measured. 精度 (seido) is the general word for “accuracy/precision,” and 歩度 (hodo) is the technical word for “rate.” You will see all three used loosely to mean the same idea.

Two things matter before you trust any of these numbers. First, a daily rate on a listing is a static, single-position, moment-in-time measurement, not a certification. Second, it is usually taken 平置き (dial-up, flat) on a timing machine, not on a moving wrist. We come back to why that gap is large — but keep it in mind as you read every figure below.

The accuracy terms you will see, translated

These are the words that appear in the accuracy line of a Japanese listing or in the caption under a timegrapher photo. Learn the six in bold and you can read almost any listing.

Japanese Reading English What it tells you
日差 nissa Daily rate Seconds gained (+) or lost (−) per 24 hours
精度 seido Accuracy / precision General term; usually points to the daily rate
歩度 hodo Rate The running rate; same idea as 日差
振動数 shindōsū Beat rate Balance frequency in vph; confirms the caliber
振り角 / 振角 furikaku Amplitude Balance swing angle in degrees; movement health
片振り kataburi Beat error Left/right timing imbalance in milliseconds
実測 jissoku Measured / actual The figure was actually measured, not quoted from spec
平置き hiraoki Dial-up / flat The position the reading was taken in
姿勢差 shiseisa Positional variation How much the rate changes between positions
タイムグラファー — Timegrapher The machine that reads the balance’s ticking

How to read a timegrapher photo on a listing

Many Japanese sellers post a photo of a タイムグラファー (timegrapher) screen. A timegrapher is a rate machine that “listens” to the balance wheel through a microphone and reports the watch’s condition in four numbers. Here is what each line on that screen means, and the range a healthy movement should fall in.

Daily rate (日差 / rate, s/day)

The headline number, in seconds per day, with a + or −. What counts as good depends entirely on the movement — a chronometer and an entry-level automatic have very different targets, covered in the table two sections down.

Amplitude (振り角, degrees)

The angle the balance swings through. A common workshop target is roughly 270°–320° at full wind, dial-up; higher amplitude means a healthier, more stable movement. Low amplitude (say under 230°) points to a tired mainspring, thickened oil, or a service coming due — even if the daily rate still looks fine. A listing that gives a daily rate but hides amplitude is telling you less than it seems.

Beat error (片振り, milliseconds)

The timing gap between the balance’s left and right swings. 0.0–0.2 ms is good; up to about 0.5 ms is often tolerated on vintage pieces. A large beat error wastes energy and can hurt timekeeping in some positions.

Beat rate (振動数, vph)

Confirms which caliber you are looking at (see the next section). It should match the movement the seller claims — a “Rolex 3235” that reads 21,600 vph on the timegrapher would be a red flag.

Beat rate (振動数) decoded: 21,600 / 28,800 / 36,000

Beat rate is how many times per hour the balance swings — written in Japanese as 28800振動 or 毎時28800振動, sometimes as 8振動 (per second). To convert, divide the hourly figure by 3,600 to get beats per second, and by two again to get Hertz.

振動数 (vph) Beats/sec Hz Label Typical calibers
21,600 6 3 Hz Low-beat (ロービート) Vintage, some Seiko
28,800 8 4 Hz Modern standard Rolex 3235, Omega, Grand Seiko 9S65
36,000 10 5 Hz Hi-beat (ハイビート) Grand Seiko Hi-Beat 9S85, Zenith El Primero

Terminology is used loosely: some Japanese sources call anything at 28,800 vph and above “hi-beat,” but in marketing “Hi-Beat” most strictly means 36,000 vph, as in the Grand Seiko Hi-Beat 36000 line. Higher beat rates can give a steadier rate but demand more from lubrication. For reading a listing, the number’s main job is to confirm the caliber.

What daily rate is “normal”? By movement type

There is no single “good” daily rate. A figure that is excellent for an entry automatic would be poor for a certified chronometer. The table below lists the published tolerances, each with its source, so you can judge a listing’s 日差 against the right yardstick. Note whether a spec is a factory tolerance or a real-world-use figure — they differ, and that difference is the whole point of the next section.

Standard / movement Rate (seconds/day) What kind of figure
COSC chronometer (ISO 3159), mechanical −4 / +6 Certification, movement, 5 positions
Rolex Superlative Chronometer −2 / +2 Certification, cased watch
Omega Master Chronometer (METAS) 0 / +5 Certification, cased watch
Grand Seiko 9S mechanical — factory +5 / −3 Mean daily rate before assembly
Grand Seiko 9S standard — in use +10 / −1 Manufacturer “normal usage”
Grand Seiko 9S hi-beat — in use +8 / −1 Manufacturer “normal usage”
Grand Seiko Spring Drive ±1/day (±15/month); best ±0.5/day Manufacturer spec
Seiko 6R mechanical (e.g. 6R35) +25 / −15 Factory spec, normal temperature

Read a listing’s daily rate against its own caliber. A Seiko 5 or 6R35 running 日差 −12秒 is comfortably within Seiko’s +25/−15 spec, not a defect. The same −12 on a serviced Rolex would suggest the watch is out of adjustment or due for attention. And a Grand Seiko listing that quotes a monthly figure (月差) rather than a daily one is almost certainly a Spring Drive or quartz model — those are rated per month, not per day.

Why the listing’s 日差 is not what you will get on your wrist

This is the single most useful thing to understand. A daily rate on a listing is measured under laboratory-friendly conditions and will drift once the watch is on you. Four reasons:

  • Static vs. worn. Grand Seiko itself publishes two numbers for the same 9S movement: a tight +5/−3 “before assembly” and a wider +10/−1 for “normal usage.” Even the maker separates the bench figure from the on-wrist figure.
  • Single position. A listing reading is usually 平置き (dial-up) only. A mechanical watch runs at different rates in different positions; the spread is 姿勢差 (positional variation). Your wrist cycles through many positions all day, so the average you experience differs from a one-position bench number.
  • Moment in time. The figure reflects that day, that wind state, and that temperature. Rate changes as the mainspring unwinds, as temperature shifts, and as the watch ages between services.
  • Not a certification. A dealer’s timegrapher reading is not a COSC, Rolex, Omega or Grand Seiko certification. It is a helpful health check, not a guarantee — and it says nothing about whether the watch is authentic. Verifying that a watch is genuine is a separate step; see our guide to authenticating a watch bought from Japan.

Worked example: reading a real-style listing line

Take a line in the style Japanese watch specialists write:

ロレックス デイトジャスト Ref.126234 / OH済 / 日差 +3秒（平置き実測）/ 振動数 28800 / 振り角 285° / 片振り 0.2

Read left to right:

  1. 日差 +3秒 — gains 3 seconds per day, measured dial-up. Rolex’s own standard is ±2 on the factory-cased test; a static dealer reading of +3 on a serviced pre-owned watch is close and healthy, not a defect.
  2. 平置き実測 — measured (not quoted) in the dial-up position only. The worn average will differ once positional variation is included.
  3. 振動数 28800 — 8 beats per second, 4 Hz, consistent with a modern Rolex caliber such as the 3235. If this read 21,600 you would stop and ask why.
  4. 振り角 285° — amplitude within the healthy 270°–320° band, so the movement has good energy.
  5. 片振り 0.2 — beat error at the top of the “good” range.
  6. OH済 — recently serviced, which is why the readings look strong; confirm the service date and provider using our service-terms guide, and cross-check the reference against the case with our Rolex reference guide.

Verdict: a healthy, recently serviced runner with numbers that hang together. The accuracy line supports the seller’s condition claim — but it certifies nothing on its own.

Green flags and red flags in an accuracy line

Once you can read the numbers, patterns jump out. Use these as a quick screen, not a substitute for inspection.

  • Green: amplitude given and in the 270°–320° band; beat error 0.2 ms or less; daily rate near the caliber’s spec; a recent OH済 service; and the word 実測 (actually measured) rather than a quoted spec.
  • Amber: a daily rate given with no amplitude — a tired movement can still show a decent rate at full wind; a single-position reading presented as if it were the worn rate; or “参考” (for reference) with no measurement.
  • Red: amplitude well under 230°; a beat rate that does not match the claimed caliber; a chronometer-grade watch running tens of seconds off with no mention of service; or a 日差 quoted for a quartz watch — quartz accuracy is stated as 月差 (monthly), so a daily figure suggests the seller is guessing.

Frequently asked questions

Is a Japanese seller’s 日差 a chronometer certification?

No. It is a workshop measurement on a timegrapher. COSC, Rolex Superlative Chronometer, Omega Master Chronometer and the Grand Seiko Standard are formal certifications with defined test protocols. A dealer’s 日差 is a useful health check, not a certificate.

My watch reads +8 seconds a day — is it broken?

It depends on the caliber. For an entry mechanical like a Seiko 6R35 (spec +25/−15), +8 is excellent. For a Rolex or Omega chronometer, +8 is outside the certified band and suggests it is due for regulation or service. Always compare against the movement’s own spec.

What is 振り角 (amplitude) and why does it matter?

It is the angle the balance wheel swings through, a direct indicator of movement health. A healthy movement sits around 270°–320° at full wind, dial-up. Low amplitude signals worn lubrication or a mainspring losing energy, and often precedes rate problems — which is why a listing that shows amplitude is more informative than one that shows only a daily rate.

Does a great 日差 mean the watch will keep that time on my wrist?

No. A listing figure is static, single-position and taken at one moment. On the wrist the watch cycles through positions, wind states and temperatures, so the average you experience will differ — sometimes by several seconds a day.

How do I read accuracy on a quartz or Spring Drive listing?

By the month, not the day. Quartz and Grand Seiko Spring Drive are rated as 月差 (monthly rate) — for example ±15 seconds per month for a standard Spring Drive. A daily rate on such a listing is a sign the seller has copied a mechanical template.

Before you trust an accuracy line: checklist

  • Identify the caliber first, then judge the 日差 against that caliber’s own spec.
  • Look for amplitude (振り角) — a daily rate alone hides movement health.
  • Check that the beat rate (振動数) matches the claimed caliber.
  • Note the position: 平置き (dial-up) is one position, not the worn average.
  • Prefer 実測 (actually measured) over quoted spec, and note the service history (OH済).
  • Treat every figure as “as of the measurement date,” and remember accuracy is not authenticity.

Key takeaways

  • 日差 (daily rate) is seconds gained (+) or lost (−) per day; 精度/歩度 mean the same idea, and it is measured on a timegrapher.
  • “Normal” depends on the caliber: chronometers run within a few seconds a day, while an entry Seiko is spec’d at +25/−15.
  • A listing’s number is static, single-position and a snapshot — Grand Seiko itself quotes a tighter bench figure and a wider in-use figure for the same movement.
  • Read amplitude (振り角, 270°–320°) and beat error (片振り, ≤0.2 ms) alongside the rate; a rate alone can hide a tired movement.
  • A dealer’s accuracy reading is a health check, not a certification, and says nothing about authenticity.

Have RYUZU read the listing with you

Accuracy numbers are only one line of a Japanese listing, and they are easy to over-read. If there is a specific reference you want, RYUZU WATCHES searches the Japanese market on your behalf and inspects the watch — including its running condition — before you commit. You get the timegrapher figures explained against the right caliber, not a screenshot without context.

Sources

This article reflects certification tolerances and caliber specifications published as of September 2026. Figures change; confirm against the primary sources below.

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