1. Which should be used in the following sentence: number or amount? Note that there are different types of metal here.
  2. Does the answer change if there's only one type of metal?

The number/amount of metals is 10 million tons.

  • 1
    You can't use "number" to refer to the weight in this context. It doesn't make sense.
    – Billy Kerr
    Nov 30, 2023 at 11:21
  • More usual would be just: 10 million tons of metal(s).
    – Lambie
    Nov 30, 2023 at 19:49

6 Answers 6


"Number" is used for countable quantities. That is, for something that can be expressed as an exact integer number. "Amount" is used for measurements, that is, things that cannot be counted exactly.

For example, you might say, "The number of people who live in my house is four." It is an exact number. It would be nonsense to say there are 3 1/2 people or 4.928 people. But you would say, "My weight is 183 pounds." It is not an exact number, but like any measurement has some potential range of error.

If you said there are four people in the room and I counted five, I would say that you are mistaken. Maybe even that you are lying, if you had a reason to lie about such a thing. But if you said your weight was 183 pounds and then you stood on a scale and it said 183.2, it would be incorrect to say that your original statement was false. It was just a less precise measurement. (Perhaps I have a better scale, or you rounded off.) It is always possible to give a more precise measurement. I suppose until you get to the point where you are measuring one atom. But at some point adding more digits becomes meaningless. If you give your height as 183.1293092930309230932902390230932 pounds, that's just nonsense. If you exhale your weight could change by more than that. If a piece of dead skin flakes off your arm your weight could change by more than that.

"Tons" is a measurement, so it is an amount.

And by the way, in American English, at least, we would say, "The amount of METAL (singular) is 10 tons", not "metals", plural. Or more likely, "The weight of the metal is 10 tons", but that's a different question.

If you had 10 different KINDS of metal, like iron and tin and copper and whatever, you could say, "The number of metals is 10." But a fluent speaker would be more likely to say, "There are 10 metals" or yet more likely, "There are ten kinds of metal."

  • 1
    "If you give your height as 183.1293092930309230932902390230932 pounds, that's just nonsense." For at least two reasons!
    – nasch
    Nov 30, 2023 at 21:00
  • But: contrast "amount" in "an amount of 10 million pounds" as in money.
    – muru
    Dec 1, 2023 at 4:46
  • 1
    "The amount of metals is 10 tons" would be correct (with the plural) if there are multiple kinds of metal, or especially if the materials were classified into multiple categories and one of the categories is "metals" Dec 1, 2023 at 13:12
  • 1
    @JiříBaum Yes, technically valid, but not something a native speaker would be likely to say. Yes, if we were talking about the amount of (various kinds of) metals and the amount of plastic and the amount of glass, yes, someone might say it in that context.
    – Jay
    Dec 2, 2023 at 2:39
  • 1
    @nasch Whoops, good point. Of course I meant if you give the VOLTAGE as 183.1293092930309230932902390230932 pounds.
    – Jay
    Dec 2, 2023 at 2:41

Definitely amount. "The number of metals is 10 million tons" makes no sense at all. "The number of metals is 10" would be perfectly correct and mean that there were 10 types of metal. The answer does not change if there is only one type of metal. "X tons" is always an amount and never a count of a number of items.

  • 7
    "The total weight of metals..." would be better. Nov 30, 2023 at 9:27

"Number" is definitely wrong in that context (the measurement isn't a count of how many metals), but "amount" doesn't sound totally natural either. (It's not wrong, but not the way I'd phrase it; Canadian anglophone here.)

You could say "the quantity of metal is 10 million tons", because weight is a quantity. I'm not sure exactly why "the amount ... is 10 million tons" doesn't sound right but quantity does; perhaps "amount" has connotations of countable rather than continuous measurements. (Like go to the metal store, "I'd like to buy some steel" / "What amount?" / "Five ingots, please".)

Note that I also didn't use plural "metals", because we're not counting how many different metals or emphasizing that there are different types. "Quantity of metal" emphasizes that we're grouping all types of metal into the category of just "metal". "Quantity of metals" sounds like it might introduce a measurement that relates to the number of different metals.

Or as Kate Bunting suggested, "The total weight of metals is 10 million tons". I think in that context, "metals" isn't a problem since "total weight" already specified we're adding up across the different kinds of metal in the collection.

  • I think "10 million tons" would be a perfectly normal answer to a question "How much metal is that?" or "What is the amount of metal needed?" Therefore tons describes an amount of metal, and "The amount of metal is 10 million tons" is fine. IMO.
    – nasch
    Nov 30, 2023 at 21:02
  • @nasch: agreed as a reply to those questions. It still doesn't sound totally natural to my ear to say "What is the amount of metal needed?" but "What amount of metal is needed?" sounds fairly ok. In all these cases we're saying "metal" not "metals". But I don't think it's just the OP's use of "amount of metals" that was making "amount" sound less natural to me. Nov 30, 2023 at 21:07
  • Yes, "metals" is a bit strange. I would only use that if it were important for some reason to stress that there are different types of metal being measured together.
    – nasch
    Nov 30, 2023 at 21:09
  • 1
    Yes, I'd have said the same... I'd use "quantity" over either "amount" or "number" in this case. Nov 30, 2023 at 21:16
  • 1
    @MessiTheMagician: If context hadn't already established that and you wanted to emphasize it, or just make sure it was unambiguous, you might say "the total weight of different metals is 10 million tons". All of the phrasings in my answer are fully compatible with there being multiple types of metal; if you wanted to convey that there was only one type, a good way to do that would be to name it: "there's 10 million tons of iron". That doesn't rule out there being other types of metal, but if you don't name any then it's at least implied. Again, lots of options depending on context. Dec 1, 2023 at 6:02

Ten million tons is a possible amount of metal. (Note the singular. It would sound odd to use a plural there.)

The only context I can think of to speak of a number of metals would be if we're talking about different kinds of metal: "Around 95 of the 118 elements in the periodic table are metals." (quoting the corresponding Wikipedia article) - In other words, the approximate number of metals in known existence is 95.

You may also note that an amount is usually given as a combination of number and unit (six kilograms; half a pint; one mole; fifty crates...), while a number is a dimensionless quantity (six; one; fifty; two thousand and seventy-four...).


I think a key part of the phrasing that other answers miss out on is that "number of metals" is providing a unit "metals", but "X tons" is also providing a unit "tons". If we changed the phrase to "The number of cows is 10 million chickens" it may be more obvious that you have conflicting units of measurement, cows vs chickens.

If you say the "amount of metals", metals is no longer a unit, it's the subject of the sentence and no longer conflicts with the other unit of measurement, tons.

  • 1
    Not necessarily. You could have a huge pile of copper and steel, whose combined weight is 10 million tons. It would not be incorrect to state that the amount of metals (because there are two metals) is 10 million tons. But it would be more common to say "metal".
    – nasch
    Nov 30, 2023 at 21:03
  • @nasch Not necessarily? Your statement completely agrees with what I said. "Amount of metal(s) (copper and steel) is 10 million tons" where "metal(s)" is the subject, not a unit.
    – B-Rad
    Dec 6, 2023 at 20:24
  1. Remove the "s" from "metals." In most cases when talking about a raw material like metal, wood, or cloth, the noun is uncountable- you can't put a number on it without some countable unit (tons of metal, meters of cloth).

  2. That should make it more clear that "The amount of metal is 10 tons" is correct. You might also say "the quantity of metal." But this sentence still sounds a bit strange to me as an English speaker, even if it's grammatically correct.

Can you give us more context around the sentence? That really affects how you say what you want to express.

Edit Based on Comments

In the case of referring to a group of multiple types of metal at the same time, saying metals is acceptable. Personally, I would still avoid the s unless you are very comfortable using it, since saying metal would be correct in either case.

I recommend something like "In 1995, Sokovia produced ten tons of metal in total"

  • I'm writing an IELTS essay. The given chart shows us information about the numbers of tons of metals (note that they used "metals" in the question) produced in different areas in the world from 1990 to 2000 and asks us to make comparisons about the trends during that period examined.
    – Ken Adams
    Dec 4, 2023 at 3:24
  • 1
    Ah, that makes sense. I assume the chart shows X tons of copper, Y tons of iron, and so on? In that case, where you are referring to a group of multiple types of metal, tons of metals is acceptable. I would still prefer to avoid the s unless you are very comfortable using it. I will update my answer.
    – automaton
    Dec 4, 2023 at 18:16

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