Switch Actuation Calculator
Put two or three switches side by side and compare actuation distance, total travel, actuation force, bottom-out force and the resulting force gradient.
Tool Operation Area
Tactile switches have a local force peak at the bump. Read the gradient as an average slope, not as instantaneous resistance.
Working Principle
A mechanical switch is a spring in a housing with a contact leaf. Two numbers describe its geometry: actuation point, the depth at which the leaf closes the circuit, and total travel, the depth at which the stem hits the bottom housing. Two more describe its resistance: actuation force, the load on the spring at the actuation point, and bottom-out force, the load at full compression. Because a coil spring follows Hooke's law over its usable range, force rises close to linearly with displacement, so the gradient between actuation and bottom-out tells you how the switch feels in the last portion of the keypress. A switch with 45 g actuation at 2.0 mm and 60 g bottom-out at 4.0 mm rises about 7.5 g per millimetre; one that rises 20 g over the same distance feels distinctly progressive and discourages heavy bottoming out. Overtravel, the distance between actuation and bottom-out, controls how much cushion you have after registering a key: a short 1.2 mm overtravel on a speed switch means presses register almost immediately but leave little margin for error, while 2.0 mm of overtravel is forgiving for typists. Tactile switches deviate from the linear model around the bump, where force peaks then drops; the calculator therefore reports the linear approximation and flags tactile entries so you interpret the gradient as an average rather than an instantaneous value.
How to Use
- 01Enter the switch name and its four spec numbers for each column. Vendor spec sheets list them as actuation/travel in millimetres and force in grams.
- 02Add a second and optional third switch to compare.
- 03Read the derived rows: overtravel, force gradient and pre-travel ratio.
- 04Note for beginners: gram figures on marketing pages are usually bottom-out force, not actuation force. Check which one you are copying.
- 05Springs in aftermarket sets are specified by bottom-out at 4.0 mm; if your switch has 3.5 mm travel the real force will be lower than printed.
FAQ
Why do my measurements differ from the vendor spec?
Manufacturing tolerance on springs is typically plus or minus 5 g, and leaf position varies by plus or minus 0.2 mm. Treat spec sheets as batch averages.
Is a lower actuation point always faster?
It shortens the registration distance but increases accidental presses. Most typists prefer 1.8-2.0 mm; speed switches sit at 1.0-1.2 mm.
How does the gradient apply to tactile switches?
It is an average slope. The tactile bump creates a local force peak that this linear model does not represent, so use the gradient only for comparing families.
Does lubing change these numbers?
Lubricant reduces friction, not spring rate. Measured force drops by roughly 1-3 g and the travel numbers stay the same.
Related Tools
Spring Swap Force Calculator
Predict actuation and bottom-out force from spring geometry.
Switch Parameter Database
Filter mainstream linear, tactile and clicky switches by force, travel and sound.
Lube Quantity Estimator
Estimate grams of lube needed for stems, springs and housings.
Switch Compatibility Checker
Verify switch, socket and plate cutout compatibility before you order.