Weighted vs semi-weighted keys: which do you need?

The short answer

If you want to learn piano properly, buy fully weighted hammer keys, ideally a graded action. Semi-weighted and synth-action keyboards are lighter, cheaper and fine for synth, organ and live arranging, but they teach the wrong touch and you will have to relearn it the day you sit at an acoustic piano. Every one of the six pianos we recommend, from the £279 Alesis Recital Pro to the £729 Kawai ES120, uses a real 88-note weighted hammer action, because that is the one specification we will not compromise on. The rest of this guide explains exactly why, and what the marketing terms really mean.

The four types of keyboard action, from lightest to heaviest

Manufacturers use a confusing tangle of names, but every keyboard action falls into one of four broad families. Understanding them is the fastest way to avoid buying the wrong instrument.

1. Synth action (unweighted)

The lightest and cheapest. A synth-action key springs back with almost no resistance, typically needing only around 30 to 40 grams of force to press, and the key returns to rest in a fraction of a second. It is built for fast organ runs, synth leads and one-finger arranger chords, not for piano technique. You find it on £100 to £200 portable keyboards with 61 keys. It is wonderful for what it is designed to do and useless for learning to play the piano.

2. Semi-weighted

A synth-action bed with a small spring or a light weight added to give a little more resistance, usually around 40 to 50 grams. It feels firmer than a pure synth key but still nothing like a piano: there are no hammers, so the key cannot reproduce the way an acoustic action pushes back harder the louder you play. Semi-weighted boards are popular with gigging keyboard players who want some resistance without the weight of a hammer action to carry. For a pianist, they are a halfway house that satisfies nobody.

3. Fully weighted hammer action

This is the real thing. A hammer action puts a small physical hammer behind every key, so pressing a note lifts a weight exactly as it does on an acoustic piano. The down-weight typically sits around 50 to 60 grams in the middle of the keyboard, and crucially the resistance changes with how fast you strike, which is what lets you play quietly or loudly with control. This is the action on every piano on this site. The Alesis uses a basic hammer bed at 7.5 kg, while the Kawai ES120 uses Kawai's Responsive Hammer Compact, the most acoustic-like action in our test.

4. Graded hammer action

The most realistic of all, and the type we rate highest. A graded action varies the hammer weight across the 88 keys: the bass notes are noticeably heavier to press, around 60 to 70 grams, and the treble notes lighter, around 45 to 50 grams, exactly as on a concert grand where the bass strings and hammers are physically larger. The Yamaha P-145's Graded Hammer Compact and the Roland FP-30X's PHA-4 are both graded, which is a large part of why they feel so convincing.

How heavy is "heavy"? The numbers that matter

It helps to put real figures on this, because "weighted" is a marketing word that can mean almost anything. A standard acoustic grand piano has a static down-weight of roughly 50 grams per key in the middle register, the force needed to start the key moving, and an up-weight of around 20 to 25 grams, the force with which it returns. A good digital hammer action aims to land in that same window. A synth-action key, by contrast, needs perhaps 30 grams and returns almost instantly; a semi-weighted key sits around 40 to 50 grams but without the dynamic response. The difference of just 10 to 20 grams sounds tiny on paper, but it is the difference you feel in the first ten minutes, and it is what builds the finger strength a pianist needs.

There is a second number worth knowing: key travel, the distance the key moves down before it bottoms out. An acoustic piano and a good hammer action travel around 10 mm, deep enough to control the note as it sounds. A toy keyboard travels far less. When the travel is too shallow, you cannot shape a note with the same nuance, which is another reason a real hammer action transfers so much better to an acoustic. Some hammer actions, including the Roland PHA-4, also add escapement, the faint notch you feel near the bottom of the travel on a grand, the small click as the hammer disengages. It is a detail, but it is the kind of detail that separates a £279 action from a £729 one.

Why graded action is worth paying for

On a real grand piano the hammers in the bass are physically larger and heavier than the ones in the treble, so a low C is genuinely harder to press than a high C. Your hands learn this from the first lesson, and that muscle memory is part of what makes a pianist a pianist. A flat, uniform weighting, where every key feels the same from bottom to top, is easier and cheaper to build but teaches your hands the wrong thing. A graded action recreates the real gradient, so the touch you build at home is the touch you will use on any acoustic piano you ever sit at. In our testing the graded actions on the Roland, Yamaha and Kawai were the most natural; the slightly springier, less graded feel of the Korg B2 was the one detail that gave away its lower price, even though it remains a genuine hammer bed.

So which should you buy?

Buy fully weighted (and ideally graded) if you or your child want to learn the piano, you plan to take grade exams, or you ever expect to play an acoustic piano. That covers almost everyone reading this page. The cost of a real 88-note hammer action has fallen so far that the Alesis Recital Pro offers one for £279, so there is rarely a good financial reason to settle for less if piano is the goal.

Semi-weighted or synth action only makes sense if you are primarily a synth, organ or live keyboard player who values light, fast keys and low weight to carry, and you have no intention of playing classical piano repertoire. Even then, many such players keep a weighted board at home for practice. For the learner, the parent buying a first instrument, or the returning player, semi-weighted keys are a false economy: they cost less today and cost you more later, when you have to relearn the touch on a real piano. That is the whole case in one sentence, and it is why our advice never wavers on this point. To see how this plays out across actual instruments, read our buying guide and our best digital piano for beginners picks.