Whether you own a luxury timepiece, a family heirloom, or a modern automatic watch, understanding how accurately it keeps time is essential. Accuracy isn’t just about convenience — it reflects the mechanical health of the watch and can help you detect when a service or adjustment is needed.

At Steven Hale Watch Restoration (SHWR), we believe every watch owner should have a good understanding of their timepiece’s performance. While professional timing machines offer the most precise measurements, it’s entirely possible to check your watch’s accuracy from the comfort of your own home.

This guide will walk you through why accuracy matters, how to measure it, and what to do if your watch isn’t performing as it should.

Why Watch Accuracy Matters

The “accuracy” of a watch refers to how closely it adheres to real-world time. All mechanical and quartz watches deviate slightly — some by seconds, others by minutes — depending on design, condition, and use.

Accuracy matters because:

• It tells you whether the watch is functioning properly.

• It indicates whether the movement is in need of lubrication or adjustment.

• It helps verify whether your vintage or luxury watch is still within factory specifications.

• It affects complications like moonphase, perpetual calendar, or alarms, which require precise timekeeping.

Acceptable Accuracy Ranges

Different types of watches are designed with different expectations:

Quartz Watches

• Typical Accuracy: ±15 seconds per month

• High-end quartz watches, like Grand Seiko’s 9F or Citizen’s Eco-Drive, can reach ±5 seconds per year.

• If your quartz watch is gaining or losing more than 20–30 seconds per month, it may need a new battery or servicing.

Automatic / Mechanical Watches

• Standard range: -20 to +40 seconds per day for most modern watches.

• COSC-certified chronometers (like certain Rolex, Omega, or Breitling models): -4 to +6 seconds/day

• Vintage mechanical watches: may be acceptable within ±1 to 2 minutes/day depending on age and condition

If your watch deviates more than expected, that doesn’t necessarily mean it's broken — it may simply be magnetised, in need of regulation, or due for its next service.

How to Test Watch Accuracy at Home

1. Choose a Reference Time Source

Before you begin, you’ll need an accurate, reliable reference. The following sources are recommended:

• Official time from the Royal Observatory: www.time.is

• BBC Time Signal (Pips): Via BBC Radio 4

• Smartphone atomic clock apps: such as “Time.is”, “Atomic Clock Sync”, or “ClockSync”

2. Synchronise Your Watch

To start, choose a moment to sync your watch to the reference time:

• Pull out the crown (or stop the seconds hand, if possible) when your reference hits the top of a minute (00 seconds).

• Set the hour and minute hands precisely.

• Push the crown back in exactly on the next whole minute from your reference source.

Make a note of the starting time, date, and even your watch’s position (dial up, crown down, etc.) — this helps you spot position-based timing variances.

3. Check After 24 Hours (or More)

After 24 hours or a few days (the longer, the better for accuracy), compare your watch to the reference time:

• Calculate the difference in seconds (either gain or loss).

• Divide by the number of days tested to determine seconds per day.

Example: If your watch is 18 seconds fast after 3 days, it's gaining 6 seconds per day.

4. Repeat in Multiple Positions

Mechanical watches often run at different rates depending on their position (e.g., dial up, crown down, crown left). You can check accuracy in:

• Dial up (flat on a table)

• Crown down (vertical, crown at bottom)

• Crown left or right

• Dial down

Watches can gain or lose a few seconds differently in each position due to gravitational effects on the balance wheel. This test can help detect if positional regulation is off.

Optional Tools for More Precise Testing

For those who want to dive deeper into accuracy testing, here are some home-friendly tools and apps:

1. Timegrapher Machines (e.g., Weishi 1000)

A timegrapher listens to the beat of the watch and displays:

• Rate (gain/loss in seconds per day)

• Amplitude (swing of the balance wheel, typically 270°–310°)

• Beat error (symmetry of the tick-tock sound)

These machines cost between £100–£300 and are a worthwhile investment for collectors.

2. Smartphone Apps

Some apps use the watch’s ticking sound via your phone’s microphone:

• WatchCheck (Android): Allows manual input of deviation over time.

• Watch Accuracy Meter (Android): Analyses tick sounds and provides estimated rate and beat error.

• Toolwatch (iOS/Android): Compares watch time to internet time sources.

Note: Accuracy may vary depending on your phone’s microphone and ambient noise.

Common Accuracy Issues and What They Mean

1. Magnetism

One of the most common causes of poor accuracy. Magnetised hairsprings cause erratic timing — sometimes gaining minutes per day.

Symptoms:

• Sudden increase in rate

• Watch runs fast consistently

Fix:

• SHWR offers professional demagnetisation in seconds using anti-magnetic equipment.

2. Low Power Reserve

If your automatic watch is not worn long enough, it may not be fully wound, affecting timekeeping.

Solution:

• Wind the watch fully (about 30–40 crown turns)

• Monitor accuracy once the power reserve is full

3. Temperature Fluctuations

Extreme changes in temperature can affect accuracy, especially in older or unregulated watches.

Solution:

• Avoid wearing the watch in extreme heat or cold

• Test accuracy in stable conditions

4. Shock or Drop

Even a small bump can affect the fine tuning of a balance spring or regulator.

Symptoms:

• Sudden drop in accuracy

• Inconsistent gain/loss per day

Solution:

• Have the watch professionally inspected and regulated

When to Seek Professional Help

Testing at home gives a helpful overview, but if you notice consistent issues or large deviations, it may be time for professional attention. SHWR recommends a service or regulation if:

• Your mechanical watch gains/loses more than 20 seconds/day

• There’s erratic timekeeping (fluctuating between fast and slow)

• You’ve noticed recent shocks or magnetism

• The watch hasn’t been serviced in 4–5 years

How SHWR Tests Accuracy

At Steven Hale Watch Restoration, we use industry-standard Swiss-made timegrapher machines and regulated test environments to assess watch accuracy. For vintage watches, we take special care to test them in multiple positions, factoring in their age and wear.

When a watch is serviced, we always:

• Demagnetise the movement

• Regulate to manufacturer specs

• Test amplitude, beat error, and power reserve

• Provide customers with detailed timing results

If your watch is not keeping time within its expected tolerance, we can usually adjust it without needing a full service — depending on its condition.

Conclusion: Keep Time Like a Pro

Testing your watch’s accuracy at home is simple, rewarding, and can help prevent larger problems from developing unnoticed. Whether you’re tracking a precision chronometer or monitoring a treasured vintage piece, a little vigilance goes a long way.

By comparing your timepiece to an official source and logging its performance over time, you’ll get valuable insight into its health and timing characteristics. If any irregularities appear, SHWR is here to help — with the tools, experience, and expertise to keep your watch ticking in perfect harmony.

Need help diagnosing a timing issue? Contact Steven Hale Watch Restoration today for professional testing, servicing, or advice tailored to your watch.