Estimate how many hours your automatic watch has left before it stops. Enter the claimed power reserve and when you last fully wound or wore it. Includes activity adjustment and a private history log.
Common values: Seiko 5 / NH35 ≈ 41h · ETA 2824 ≈ 38–42h · Rolex ≈ 70h · Grand Seiko ≈ 72h
No previous calculations yet.
The tool starts with the manufacturer’s claimed power reserve and subtracts the time that has already passed. It then adjusts the remaining estimate according to your activity level, because wrist movement partially rewinds the mainspring.
The result is a practical estimate. Real-world power reserve can vary due to how fully the watch was wound, the position it rests in, temperature, and the condition of the lubricants.
• Laboratory tests are done under ideal conditions
• A partially wound mainspring delivers less than the full rating
• Different positions (dial up, crown down) change the running time
• Older oil and lower amplitude reduce efficiency
• Temperature affects the movement
How accurate is this power reserve tracker? It gives a useful real-world estimate. For most watches in good condition it is typically within a few hours of the actual stopping time when activity is judged correctly.
Should I wind the watch fully before starting a test? Yes. For the most meaningful result, fully wind the watch (or wear it until the power reserve is topped up) and then start the timer.
Does wearing the watch keep it running longer? Yes. The rotor winds the mainspring through normal movement. Higher activity levels increase the effective remaining runtime.
What if my watch stops earlier than predicted? This can indicate the movement needs service, the mainspring was not fully wound, or the activity level was overestimated.
Is the history saved on your servers? No. Everything is stored only in your browser (localStorage). Nothing is sent to any server.