Actuation Force vs Bottom-Out Force, Explained

When you read a switch spec sheet, the first number you see is usually the actuation force — something like “45g.” It feels like the headline stat, the one that tells you how heavy a switch is. The problem is that for most people, most of the time, it’s the wrong number to fixate on.

The number you actually feel under your fingers is the bottom-out force, and switch makers don’t always advertise it prominently. Understanding the difference will change how you read every spec sheet from here on.

Two Different Moments in One Press

A keypress isn’t a single event — it’s a journey. The spring resists more and more as you push the stem down, so the force required changes throughout the travel.

• Actuation force is how hard you press at the exact moment the key registers — partway down the travel.
• Bottom-out force is how hard you press when the stem hits the very bottom.

Because the spring keeps compressing, bottom-out force is always higher than actuation force. The gap between them depends on the spring.

Why Bottom-Out Is What You Feel

Here’s the part that surprises people: most typists bottom out on nearly every keystroke. We slam the key all the way down out of habit, which means the force we actually experience is the bottom-out force, not the actuation force.

So a switch advertised at “45g actuation” might bottom out around 60g — and that 60g is what your fingers register all day. Two switches with identical actuation numbers can feel completely different if their bottom-out forces differ.

A Quick Illustration

Consider two hypothetical switches with the same actuation spec:

Switch	Actuation	Approx. bottom-out	How it feels
Switch A	~45g	~55g	Light, gentle through the press
Switch B	~45g	~67g	Light to start, firm at the bottom

Same headline number, noticeably different experience. If you only read actuation, you’d expect them to feel identical — and you’d be wrong.

When Actuation Force Does Matter

Actuation isn’t useless. It matters most if you’re a light typist who genuinely doesn’t bottom out — some fast touch typists and gamers float their presses, registering keys without slamming them home. For them, actuation force is the relevant number and a lighter actuation can mean faster, less fatiguing input.

It also matters for accidental presses: a very light actuation force is easier to trigger by mistake, which is why some people find ultra-light switches twitchy at first.

How to Read a Spec Sheet Now

Going forward, treat actuation as a starting point and hunt for the bottom-out figure. If a listing only gives actuation, look for a force curve — a graph showing resistance across the whole travel. The force curve tells the full story that a single number can’t: how the resistance builds, whether there’s a tactile bump, and where the press ends up.

When two switches list the same actuation, don’t assume they feel the same. Check the spring weight, look for the bottom-out number, and read a force curve if one exists.

The Takeaway

Actuation force is the moment a key registers; bottom-out force is how hard you press when the key lands — and since most people bottom out constantly, the second number is the one you actually feel. Read past the headline spec, find the bottom-out figure or the force curve, and you’ll predict how a switch feels far more accurately than the marketing number ever could.