How much force does a soap pump take?

A stiff soap pump is treated as a small annoyance. Nobody has published what one actually takes to press. So I measured three, and the answer is about 28 newtons — roughly the weight of a 3 kg bag of potatoes, pushed straight down with one fingertip.

Why this is worth measuring

When somebody says they cannot work a soap pump, the usual reply is to press harder, use two hands, or buy a different soap. All three assume the problem is the person.

Nobody publishes the number. Manufacturers do not print it on the bottle. Occupational therapists advising on daily-living equipment have no figure to work from, and neither does anyone deciding whether an adapter is worth £9.99.

A measured figure settles two things at once: how much force a pump asks for, and whether that figure moves depending on who is pressing.

Method

Equipment. An AccuWeight digital kitchen scale.

Set-up. Every bottle was full. Each was stood upright on the scale, on a worktop, with the scale zeroed before each press.

The press. One straight downward push on the bare pump head, through to the point where the pump delivered soap. The whole stroke, not the first resistance.

What was recorded. The highest figure the scale showed during the press, in grams.

Who pressed. Two people pressed every bottle, once each — six bare readings from three bottles. One of the two has neuropathy. The other has no hand problems.

Which reading in a pair came from which person is not recorded, so the two are labelled only A and B within each bottle, and the letters do not track the same person from one bottle to the next. Nothing below depends on it: the comparison that matters is the gap between a pair, not the direction of it.

The Cussons was then pressed once more with a PALM disc fitted over the head. Which of the two made that press is not recorded either. The other two bottles were not tested fitted.

Conversion. Grams to newtons at standard gravity: N = g × 9.80665 ÷ 1000. A scale reads mass; what is wanted is the force that mass corresponds to.

Results

Seven presses, three bottles, every bottle full, all on the kitchen scale. A and B are the two people, and the letters are per bottle only — they are not known to be the same person from one row-pair to the next. Across the six bare readings: lowest 27.44 N, highest 29.24 N, mean 28.31 N. Per bottle, bare: Cussons 29.06 N, Baylis & Harding 28.33 N, Carex 27.55 N.

Analysis

The brands agree with each other

Three unrelated supermarket products, bought separately, sit within 1.8 N of one another — 6% of the mean. Carex is the lightest and Cussons the stiffest, and the gap between them is small enough that swapping brand would not rescue anybody who cannot manage one of them.

That makes about 28 newtons a usable general figure for a supermarket hand-soap pump, rather than a fact about one bottle.

Two different people got the same number, on every bottle

This is the result worth having. Every bottle was pressed once by each of two people. One of them has neuropathy; the other has no hand problems.

The widest they ever disagreed was 38 g — about 1% of a reading close to three kilograms.

That closes off the obvious objection. It would be reasonable to expect a pump to give way sooner for somebody whose hands work normally, and for the number to come out lower. It did not, on any of the three.

Put that beside the brand agreement and the conclusion is firm: the force belongs to the pump. It is set by the spring, the seal and the valve, and the person on the other end does not change what it asks for. A stronger hand does not make a stiff pump softer — it has more in reserve.

This is why advice aimed at the person misses. The pump has already set the price. The only thing still open is what you pay it with.

The force is the same. The experience is not.

Those two facts sit together and they are the whole reason this product exists.

Twenty-eight newtons is twenty-eight newtons whoever leans on it — the measurements say so. What is not the same is what those newtons feel like arriving on one fingertip, and that does depend on the hand.

Which means the thing worth changing was never the force. It was where the force lands.

Does the adapter change the force?

I measured it rather than argued it. The Cussons pump with a PALM disc fitted over the head read 2,938 g — 28.81 N. The same bottle bare read 2,944 g and 2,982 g.

The fitted reading is 6 g from the nearer bare one. That is 0.20%. The two bare presses, made by two different people on that same bottle, are 38 g apart — 1.29%.

So the difference between two people pressing the same bare bottle is 6.3 times larger than the difference the adapter makes. The adapter's effect on force is smaller than the spread the method itself produces. That is the honest way to say there is no measurable difference, without claiming it is exactly zero.

Why it lands there is geometry. There is no lever in the disc, no pivot and no linkage — it sits over the pump head and passes a straight push straight down, so the mechanical advantage is exactly 1.00. The measurement and the mechanics agree, which is the outcome you would want and not always the one you get.

Only the Cussons was tested with the disc fitted, once. That is enough to show the adapter does not take force off a pump. It is not three bottles' worth of fitted data and should not be read as such.

It would be easy, and more profitable, to imply otherwise. An adapter that made a stiff pump lighter would be a better product than the one I sell, and it is not what this is. What this is, is a bigger thing to press — so the same force can come from a palm, a fist or a forearm, where a fingertip would have given up first.

Somebody else's instrument, on somebody else's bottles

Everything above is mine: my bottles, my scale, my two pressers. That is the weakest thing about it. A single person measuring the thing his own product addresses is exactly the arrangement a reader should be suspicious of.

So here is the same quantity measured by somebody with no connection to me, on a better instrument, years before this product existed.

A YouTube channel called Mechanical Testing published Compressive force required to Press dispense the lotion pump / sanitizer bottle in June 2020. Four pump bottles were pressed under a Shimadzu universal testing machine — a bench load frame with a load cell, which is the proper instrument my kitchen scale is standing in for — and the press force for each was captioned on screen.

Their captions do not agree with themselves about units

Two of the four are labelled kg and two kgf. A kilogram is a mass; a kilogram-force is the force that mass exerts under standard gravity. They are not the same kind of quantity, and the captions use both words for what is plainly one measurement.

I have read all four as kgf, which is the reading that makes the numbers forces at all. That is the same assumption this study already makes about its own equipment — a kitchen scale reads mass, and every newton figure above is a mass reading converted at standard gravity. The conversion is shown so anyone who disagrees can redo it: N = kgf × 9.80665.

Their numbers are left as they were captioned. Correcting somebody else's labels without saying so would be the same failure this page exists to avoid.

What this supports

Four bottles measured on a load frame fall between 12.75 and 37.27 newtons — roughly 13 to 37 N. My headline figure of 28.81 N sits inside that band.

That is worth having. It comes from a different instrument, different bottles and a person who has never heard of me, and it puts the order of magnitude beyond argument: a consumer pump asks for tens of newtons, not a couple and not hundreds. If my kitchen-scale method were producing figures that were badly wrong, this is where it would show, and it does not.

What this does not support

Being exact about this matters more than the corroboration does.

• It does not verify my bottles. Cussons, Baylis & Harding and Carex were not among the four. Nothing here confirms any individual reading in my table.
• It does not verify my method. A load frame applies a controlled, measured compression. A person pressing a bottle standing on a kitchen scale does not. Agreement on the order of magnitude is not agreement on the technique.
• It does not verify the agreement between my two pressers. That result is about two people pressing the same bottle, and a testing machine pressing four bottles once each has nothing to say about it. It rests entirely on my own readings.
• It says nothing about the adapter. No disc was fitted to anything in that video.
• It is a video on a YouTube channel, not a published paper. It has not been peer reviewed and no method write-up accompanies it. There is no stated bottle fill, no stated press rate, no repeat count and no calibration record. Describing the equipment as a professional testing machine is accurate; describing the video as a study would not be.
• It is six years old. Published June 2020, so these are not fresh readings and pump designs may have moved since. It also means the measurements predate this product entirely, which is the reason they are worth citing: nobody was measuring anything to help me.

A wider band from a better instrument, and my own figure inside it. That is the whole claim.

The bed of nails concept

Stand on a single nail and it goes through your foot. Lie down on a bed of a thousand and you get up unmarked. Your weight is identical in both cases. What changed is how many points are sharing it.

What damages you is not force. It is pressure — force divided by the area it is spread across.

A bare soap pump top is the single nail. It is about the size of a 5p coin and it is asking one fingertip to take the whole 28 newtons.

This is where the product came from. I had a pump I could not work, thought about why a bed of nails does not kill anybody, and printed a disc.

What a wider surface changes

The disc takes nothing off the 28 newtons, as the measurement above shows. It changes the denominator.

So ten to twenty times less pressure on the skin, for exactly the same push.

The disc is 62 mm across, which is 30.2 cm² of face. I have used 20 cm² because a palm does not land flat on all of it, and the cautious figure is the one worth quoting. That disc is the PALM: one is £9.99, and the fit guide tells you in a minute whether it goes on the pump you already have.

The one option that changes the force

Everything above is about moving the same 28 newtons onto more skin. There is one common fix that does something different: a foaming pump pushes soap and air through a mesh rather than thick liquid through a narrow valve, and it has a genuinely lighter action.

That makes it the better answer for anyone whose problem is the force itself rather than where it lands. It costs about two pounds, I do not sell one, and I earn nothing from saying so. All six options are compared here, including where mine loses.

Limitations

Stated once, here, rather than hedged through the text.

• Three bottles, two bare presses each. Seven readings is enough to show that three brands agree, that two different people get the same number, and that fitting the disc does not change what the pump asks for. It is not enough to put a tolerance on “about 28 newtons” across the market.
• No bottle was pressed twice by the same person. Every pair is two different people, so what is measured here is agreement BETWEEN people, not the repeatability of one person's press. Those are different things and only the first is evidenced.
• Two people is two people. One has neuropathy and one does not. That is a fact about these six readings. It is not a general statement about what anybody's hands can do, and nothing here should be read as one.
• One bottle was tested with the adapter, once. The fitted result is a single reading on the Cussons. It is consistent with the mechanics and with the bare readings either side of it, and it is still one reading.
• All three are supermarket liquid hand soaps. Lotion, sun cream and washing-up liquid are thicker or have different valves, and nothing here measures them.
• A kitchen scale reads mass, not force. The conversion assumes standard gravity, which is fine, and it assumes the press is straight down, which is what was done.
• The contact areas are estimates. The force figures are measured; the pressure figures inherit whatever error is in the areas, so treat 10–20× as an order of magnitude rather than a precise ratio.
• Two of the three bottles were pressed by one person. The two-person comparison exists only for the Cussons.
• The third-party readings are a corroboration, not a replication. Different bottles, a different instrument and a different operator, with no method write-up published alongside them. They put my figure in a plausible band. They do not check any reading in my own table.

Revision history

• Version 1.1 — 31 August 2026. Added third-party corroboration: four bottles measured by Mechanical Testing on a Shimadzu universal testing machine, 12.75 to 37.27 N, with the kg/kgf caption inconsistency noted and what it does and does not establish set out. Added an Instrument column to the results table. No reading, figure or conclusion from version 1.0 was changed.
• Version 1.0 — 22 August 2026. First publication. Seven presses, three bottles, two pressers, one fitted with the disc.

PALM is a daily-living aid, not a medical device. It does not treat, prevent or improve any condition, and nothing here is medical advice. The force figures in the results table are my own measurements, taken by the method described above; the third-party figures are Mechanical Testing's and are labelled as theirs throughout. Version 1.1, 31 August 2026.