Glossary
Lift angle
Definition
The angle through which a balance wheel turns while the escapement is delivering impulse, entered into a timing machine so it can calculate amplitude from the sound of the movement.
On this page (5 sections)
A timing machine cannot see the balance wheel. It listens to the escapement through a microphone and works everything out from the timing of three sounds per beat. Rate and beat error fall straight out of that. Amplitude does not.
To derive amplitude, the machine needs to know how much of the balance's swing is taken up by the impulse itself. That figure is the lift angle, and it is a property of the specific caliber, published by the movement maker. Fifty-two degrees is the most common value, but real calibers range from the high forties to the high fifties.
What the angle describes
Follow one beat. The balance swings back toward its rest position, the impulse pin on its roller enters the notch of the pallet fork, unlocks the fork, receives a push from the escape wheel through the fork, and leaves the notch on the far side. The lift angle is the total rotation of the balance across that whole engagement, from unlocking to release, and it is set by geometry: the pallet fork proportions, the diameter of the roller, the position of the impulse pin, the escape wheel tooth form.
Two consequences follow. It is a constant of the design, so it does not change with servicing, oil, temperature, state of wind or how well the watch is running. And it is not something anyone adjusts. A watchmaker regulates rate, corrects beat error and diagnoses amplitude; nobody sets a lift angle. Swiss lever escapements in wristwatches sit broadly between the high thirties and the high fifties, with most modern calibers between 49 and 53 degrees.
Published values
These come from the manufacturers' own technical communications and technical guides, which is where any figure you use should come from.
| Caliber | Published lift angle |
|---|---|
| ETA 2824-2 | 50 degrees |
| ETA 2892-A2 | 51 degrees |
| Sellita SW200-1 | 50 degrees |
| Sellita SW300-1 | 51 degrees |
| Valjoux 7750 | 49 degrees |
| Miyota 8215 | 49 degrees |
| Miyota 9015 | 51 degrees |
| Seiko NH35 | 53 degrees |
Notice that not one of them is 52, the value most machines ship with as a default.
Why getting it wrong matters
The relationship is not small. In the model timing machines use, the reported amplitude is very nearly proportional to the lift angle you enter, so an error of ten percent in the angle is an error of about ten percent in the answer, and it runs in the obvious direction: enter too large a lift angle and the machine flatters the watch.
Put numbers on it. A movement genuinely swinging 270 degrees, measured with its true lift angle of 44, reads about 320 if you leave the machine on 52. That is the difference between a normal reading and one that suggests the balance is about to start knocking, in a watch that has not changed at all. Run the error the other way and a healthy 290 can appear as 245, which is the reading that sends people to a watchmaker asking for a service they do not need.
It is also the single most common reason two people comparing readings on the same watch disagree, and the reason a reading copied from a forum post is worth nothing without the setting that produced it.
If you cannot find the figure
Look first at the maker's technical communication or technical guide for the caliber, which is a public document for ETA, Sellita, Seiko Time Module and Miyota. Many timing machines also carry a built-in caliber list, though those lists are compiled by the machine's manufacturer and are worth checking against the source.
If nothing is published, do not borrow a value from a caliber that merely looks similar; a modified escapement changes it. Say the figure is unknown, and compare readings only against themselves, in the same position and at the same state of wind, where a trend still tells you something even when the absolute number does not. Watchmakers who need the absolute number determine it empirically, by measuring the swing optically and then adjusting the entered angle until the machine agrees.
What it is not
Lift angle is not amplitude. Amplitude is how far the balance swings, typically 270 to 310 degrees dial up at full wind; lift angle is the small slice of that swing during which the escapement is in contact, and the two are related only through the machine's arithmetic. It is not beat error, and it is not a measure of quality: a caliber with a 49 degree lift angle is not better made than one with 53.
It also assumes a lever escapement. A co-axial or other non-lever escapement has its own published figure and its own acoustic signature, and some machines read them poorly whatever you enter. Our timegrapher reading explainer covers what the numbers mean once you trust them, and timing your own watch covers doing it without a machine at all.
Last reviewed 4 September 2026. Spotted an error? Tell us and we will fix it in public.