rule of thumb
/ruːl əv θʌm/
Meaning
A broad, general rule or principle based on experience and practice rather than precise scientific calculation. It is a useful guide that works in most situations, even if it is not 100% accurate in every single case.
Examples
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As a general rule of thumb, you should save about twenty percent of your monthly income.
As a general rule of thumb, you should save about twenty percent of your monthly income.
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A good rule of thumb for baking is to always preheat your oven before mixing ingredients.
A good rule of thumb for baking is to always preheat your oven before mixing ingredients.
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My rule of thumb is to never send an email when I'm feeling angry.
My rule of thumb is to never send an email when I'm feeling angry.
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There's no strict law, but the rule of thumb is to arrive ten minutes early for an interview.
There's no strict law, but the rule of thumb is to arrive ten minutes early for an interview.
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When traveling, a useful rule of thumb is to pack light and buy what you need there.
When traveling, a useful rule of thumb is to pack light and buy what you need there.
Common Mistakes
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✗ According to the thumb rule, you should drink eight glasses of water a day.
✓ As a general rule of thumb, you should drink eight glasses of water a day.
Learners often translate this literally from other languages as 'thumb rule', but the correct English idiom is always 'rule of thumb'.
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✗ This is a very strict rule of thumb that everyone must follow.
✓ This is a good rule of thumb that most people follow.
A 'rule of thumb' is by definition approximate and practical, not a strict, legally binding rule.
Related Expressions
Practice
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As a good ___, you should always double-check your work before submitting it.
💡 A practical general guideline
Show answer
rule of thumb
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There is no official policy, but the ___ is to dress business-casual on Fridays.
💡 An unwritten, practical rule based on experience
Show answer
rule of thumb