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Business idiomsnoun phrase (idiomatic) · /ˌruːl əv ˈθʌm/

rule of thumb

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In simple English

A rule of thumb is a practical guideline that works in most situations. It's based on experience rather than precise measurement. Teams use it for quick estimates and decisions.

Someone heard this phrase in a meeting and wants to know what it means.

At a glanceCEFR B1–B2
Commonness
Versatility
FormalityCasualFormalNeutral
Spoken ↔ WrittenSpokenWrittenBoth
Directness ↔ DiplomaticDirectDiplomaticNeutral
Region

Say it like this

✓As a rule of thumb, we double our initial time estimate.
✓My rule of thumb is one test per public method.
✓A good rule of thumb is to keep functions under 50 lines.
✓There's no hard rule, but as a rule of thumb, we deploy on Tuesdays.
✓Rule of thumb: if it takes more than 3 days, break it into smaller tasks.

Real examples

Standup

"As a rule of thumb, if a task is taking longer than expected, I flag it early."

Slack message

"Rule of thumb: always test locally before pushing to staging."

GitHub PR

"A good rule of thumb is to keep PRs under 400 lines for easier review."

Jira ticket

"As a rule of thumb, we should allocate 30% of the project timeline for testing and QA."

Retrospective

"Our rule of thumb for story points worked well this sprint."

Sprint planning

"As a rule of thumb, we can handle about 40 story points per sprint."

Pair programming

"My rule of thumb is to switch drivers every 15 minutes."

Don't say this

✕The rule of thumb says we must do it this way.
✓As a rule of thumb, we usually do it this way.— A rule of thumb is flexible, not mandatory. Avoid 'must' with this phrase.
✕I have a thumb rule for this.
✓I have a rule of thumb for this.— The correct phrase is 'rule of thumb,' not 'thumb rule' in standard English.
✕By rule of thumb, we deploy on Fridays.
✓As a rule of thumb, we deploy on Fridays.— Use 'as a rule of thumb' not 'by rule of thumb.'

Other forms

noun phrase

rule of thumb

"That's a useful rule of thumb for estimation."

prepositional phrase

as a rule of thumb

"As a rule of thumb, we add 20% buffer time."

adjective form

rule-of-thumb

"This is just a rule-of-thumb estimate."

Often used with

good rule of thumbEmphasizes the guideline is useful and reliable.
general rule of thumbA broad guideline that applies in most cases.
as a rule of thumbThe most common way to introduce this phrase.
follow a rule of thumbTo use this guideline in your work.
simple rule of thumbA guideline that is easy to remember and apply.

Similar words

guidelineMore formal; often used in documentation.
heuristicTechnical term; common in engineering and UX.
best practiceImplies industry-wide acceptance, more formal.
rough estimateFocuses on approximation rather than guidance.
general principleBroader and more abstract than rule of thumb.

Opposites

hard rulestrict requirementexact calculationprecise measurementformal policy

More words

best practiceestimateguidelinebufferballparkrough estimateheuristic

Questions

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