To calibrate is to compare what an instrument shows with a reference you trust, and write down the difference. What you do about that difference is a separate decision. Turning a screw or pressing a button so the instrument reads “right” has its own name: adjustment.

That sounds like hair-splitting until you see what the written record protects. Without it, you end up with an instrument that reads differently and no way to tell whether it reads better.

What does calibrate mean in plain words?

Three moves, in this order.

Compare. Put the instrument next to a reference whose value you trust, such as a certified test weight on a scale.
Record. Write down what the instrument showed, what the reference was, the difference, and how sure you are about that difference.
Decide. Leave it alone, correct your readings using the record, adjust the instrument, or take it out of service.

Calibration is moves one and two. Move three uses the calibration. It is not the calibration.

What does the official measurement dictionary say?

Metrology is the science of measurement and its application. Its reference dictionary is the International Vocabulary of Metrology, known as the VIM. It is maintained by the Joint Committee for Guides in Metrology and published through the BIPM, the International Bureau of Weights and Measures, which looks after the international system of units. The current edition is JCGM 200:2012.

The VIM defines calibration in two steps. First, establish the relation between the values given by measurement standards (references with a known value and a stated uncertainty) and what the instrument indicates. Second, use that relation to turn future readings into measurement results. The output can be a statement, a table, a curve, or a simple correction such as “subtract 2 grams.”

Then it adds a warning: “Calibration should not be confused with adjustment of a measuring system, often mistakenly called ‘self-calibration’, nor with verification of calibration.”

Adjustment is the “set of operations carried out on a measuring system so that it provides prescribed indications corresponding to given values of a quantity to be measured.” In plain words: you change the instrument so it shows the right number. The note underneath is blunt. Calibration “is a prerequisite for adjustment,” and after an adjustment the system usually has to be calibrated again.

Verification is a third job: “provision of objective evidence that a given item fulfils specified requirements.” That is the pass or fail question. In legal metrology, the part of measurement that the law regulates, verification also means examining the instrument and marking it or issuing a certificate. In the Netherlands, for example, the government inspects the scales shops use and the pumps at fuel stations.

Calibration, adjustment, verification: what is the difference?

Step	The question it answers	What you end up with	On a kitchen scale (hypothetical)
Calibration	How far off is it, and how sure are we?	A record of the difference and its uncertainty	A 500 g test weight reads 512 g. You write that down.
Adjustment	Can we make it read right?	A changed instrument, which then needs a fresh calibration	You adjust the scale until 500 g reads 500 g, then check it again.
Verification	Does it meet the requirement?	A pass or a fail, sometimes with a mark or certificate	Is a 12 g error allowed for what this scale is used for?

The order matters. An adjustment made without a calibration is a guess with a screwdriver. The VIM’s own annotation calls calibration “a prerequisite for verification” too, because a pass or fail needs a measured difference to judge.

One practical detail. The VIM lets a calibration take the form of a table or a curve, and a table needs more than one row. A scale that is 12 g high at 500 g could, in principle, be spot on at 100 g and further off at 2 kg. One check point tells you about one point.

Why do dictionaries say calibrate means adjust?

Because in everyday English it often does. Merriam-Webster lists both senses side by side: “to standardize (something, such as a measuring instrument) by determining the deviation from a standard so as to ascertain the proper correction factors” and “to adjust precisely for a particular function.”

That is fine in conversation. It stops being fine where the word carries weight: on a certificate, in a lab report, in a contract, or on a device labeled “self-calibrating.” By the VIM’s definitions, a button that makes a device agree with its own internal setting is closer to adjustment.

A useful test: ask for the record. If nobody can show what was compared, against what, and how far off it was, something may have been adjusted. It was not calibrated in the measurement sense.

What are the everyday meanings of calibrate?

Three senses cover most of what people mean. All three start with a comparison. They differ in what counts as the reference.

Sense	You compare…	…against this reference	The record looks like
Instruments	what the device shows	a measurement standard of known value	a certificate, table or curve
Forecasts and judgment	how confident you said you were	how often you turned out to be right	a log of predictions, percentages and outcomes
Reading people	how someone looks and sounds now	how they usually look and sound	notes on their normal state

Forecasts and judgment. Here calibration means the match between confidence and accuracy. If you are well calibrated, about nine in ten of the things you call “90% sure” come true. What calibration means covers this sense in depth.

Reading people. In NLP courses (neuro-linguistic programming, a coaching method), calibration “means detecting differences” in someone’s face, voice or posture compared with how they normally are. This page only records how the word is used there. It does not assess the method.

How does the instrument idea apply to judgment?

Map the parts one to one.

The instrument is your stated confidence: “I’m 90% sure.”
The reference is what actually happened, across many calls.
Calibration is comparing your 90% calls with how often they came true, and writing the result down.
Adjustment is changing how you state confidence next time.

Most people skip straight to adjustment. After a painful miss they resolve to “be more careful,” which moves the dial without ever reading it. Knowing that overconfidence exists does not tell you how far off your own confidence is on a given day.

The Calibrated Mind gives a concrete version of the right order. Suppose your 90% calls come true 75% of the time, and that group holds twenty or more resolved calls, not four. Then the correction is: next time you feel 90%, say 80%, and check whether that reads truer. Compare, record, then decide, applied to a person.

What is CALIBRATE?

CALIBRATE is a nine-step system for matching how sure you are to what your evidence can carry. It comes from The Calibrated Mind by Len P. van der Hof, available in English and Dutch. You do not need the book to use it. The steps below are enough to start.

Calibrate confidence. Turn a feeling of certainty into a number you can check later.
Assess assumptions. List the hidden premises under your judgment and test the weakest one.
Lean on probabilities. Replace words like “likely” with numbers and ranges.
Investigate alternatives. Build the strongest case against your own view.
Build updating rules. Decide in advance how much new evidence should move you.
Record and review. Keep a prediction journal and score it.
Act with appropriate uncertainty. Set a threshold for acting instead of waiting for certainty.
Teach and extend. Explain your numbers to someone else. The gaps show fast.
Evolve your model. Review on a rhythm, because calibration drifts.

The CALIBRATE framework page has the book’s own one-line summaries.

A worked example: step 1 on a supplier promise

Step 1 is where the instrument idea starts. The book’s quick version has four moves: name the claim, read the temperature, convert it to a number, write it down.

Imagine a small company waiting on a supplier.

Name the claim so that reality can settle it: “The March order arrives by 15 March, judged by our goods-received log.”
Read the temperature. Warm, not hot.
Convert it to a number with a bet test. Would you risk four to win one on it? That bet only pays off if you are above 80% sure. No. Three to win one, which needs 75%? You hesitate. Call it 70%.
Write it down, with today’s date.

That line is not yet a calibration. It is one reading. The calibration happens when twenty lines like it have resolved and you compare your 70% calls with how often they came true. Only then do you decide whether to adjust.

What is calibration not?

Not adjustment. Adjustment changes the instrument. Calibration reads it.
Not a one-off. The VIM expects a new calibration after an adjustment. Judgment drifts too.
Not the same as being right. A well-calibrated forecaster who says 70% is wrong about three times in ten. That is the number working, not failing.
Not the whole of good judgment. Two people can be equally well calibrated while one is far more useful, because she can tell her 90% cases from her 55% cases. Calibration techniques for founders has five practices that fit a normal week.

Try this today: a ten-minute calibration record

Pick one number you estimate often: how long a task takes, how many sign-ups a campaign brings, when a supplier delivers. Find five recent cases where you know both the estimate and the outcome.

Case	What I estimated	What happened	Difference	Decision
1
2
3
4
5

Fill in the first four columns before you touch the last one. That part is the calibration. Then choose: adjust (change how you estimate), correct (keep estimating the same way and add the margin you found), or accept (the differences are noise).

Compare, record, then decide. In that order, on a scale or on yourself.

Cite this:What does calibrate mean? Compare, record, then decide: calibration is not adjustment.Len P. van der Hof. https://lenvanderhof.com/en/blog/calibrate-meaning/ · Published 2 October 2026.

What does calibrate mean? Compare, record, then decide: calibration is not adjustment