B2idiomstudyIELTS-friendly
a rule of thumb
USUK
a simple practical guide that is not exact but works most of the time
'As a rule of thumb' opens a rough guide. 'Thumb' stays singular, and the idiom is the same in British and American English.
In context
As a rule of thumb, you need about ninety hours of study to pass this exam.
A good rule of thumb is to review new words after one day and again after one week.
Common mistake
Incorrect: As a rule of thumbs, check your answers twice.
Correct: As a rule of thumb, check your answers twice.
More idioms about study
- a bookworma person who loves reading and reads a lot
- a bright sparksaid ironically about someone whose clever idea was actually silly
- a closed booka subject that you do not understand or know anything about
- a crash coursea short course that teaches a lot in a very short time
- a dab hand at somethingvery good at a particular skill or activity