Use fewer with things you can count individually.

• Fewer people attended.
• We need fewer chairs.
• There are fewer cars on the road.

Use less with uncountable quantities.

• I need less water.
• Try to use less sugar.
• We have less time.

Easy way to remember

Fewer = countable things.
Less = uncountable amounts.

There are some established exceptions in everyday English, such as less than £10 and less than five years, so don’t treat the rule as absolute.