Use "fewer" for countable things — items you could count one by one ("fewer apples", "fewer people"). Use "less" for uncountable things — quantities you measure rather than count ("less water", "less time"). The classic exception: "less" is standard for units of measurement, distance and money even though they involve numbers ("less than 10 miles", "10 items or less" is common but "fewer" is technically preferred).
This is one of the most-corrected mistakes in English, largely thanks to supermarket "10 items or less" signs — grammatically, that should be "10 items or fewer." Here's the actual rule.
The core rule: countable vs uncountable
- Fewer is for things you can count individually: fewer books, fewer mistakes, fewer people, fewer opportunities.
- Less is for things you measure as a whole, not as separate units: less water, less time, less noise, less traffic.
A simple test: if you can put a number directly in front of the word ("three books", "five mistakes"), use fewer. If it sounds odd with a number ("three water"), use less.
The tricky exception: quantities that feel countable but aren't
Distances, amounts of money, weights, and spans of time are usually treated as single units, not as a collection of countable items — so "less" is standard even though a number is involved:
- "It's less than 10 miles away." (a distance, treated as one span, not ten separate miles)
- "I have less than $20." (an amount, not twenty separate dollars)
- "The job took less than three hours." (a duration)
This is why "10 items or less" sounds natural to most people despite being technically "incorrect" by the strict countable/uncountable rule — items ARE individually countable, so purists say "10 items or fewer" is correct, but "less" has become so standard in this exact phrase that many style guides now accept it.
Quick reference
- Fewer people, less crowding
- Fewer calories, less sugar
- Fewer cars, less traffic
- Fewer emails, less inbox stress
Frequently Asked Questions
Is "10 items or less" grammatically correct?
Strictly, "10 items or fewer" is correct since items are countable — but "10 items or less" is so widely used it's now accepted as standard in everyday and even some formal usage.
Why is it "less than 10 miles" and not "fewer than 10 miles"?
Distances, money, weight and time are usually treated as a single measured quantity rather than a collection of countable units, so "less" is standard even though a number is involved.
Is it "fewer people" or "less people"?
"Fewer people" is correct — people are individually countable. "Less people" is a common mistake, though you'll hear it often in casual speech.