Fit vs. Fitted
Cambridge lists fitted as the general past form and fit as an additional US past form; fitted also remains standard in installation senses. The guide keeps tense, participle, regional, and sense boundaries explicit rather than reducing the pair to a blanket substitution rule.
“Fitted” is standard as the past tense and participle; US English also commonly uses “fit” in size/suitability senses. Installation uses strongly favor “fitted.”
Key details
Choose the right form
| Meaning / situation | Form / construction | Decision |
|---|---|---|
| general past/participle form | fitted | Use the broadly standard past form. |
| US size or suitability sense | fit or fitted | US English also commonly allows “fit” as a past form in these senses. |
| installation or equipping sense | fitted | Prefer the documented “fitted” form. |
Quick tests
Meaning / construction test
Is the past-tense use about installing or equipping something rather than merely size or suitability?
If yes: Use “fitted.”
If no: For size/suitability, “fitted” is standard and US English can also use past “fit.”
Caveat: Cambridge lists “fitted” generally and an additional US past “fit”; the acceptable past form depends partly on sense and regional usage.
Examples
The technician fitted a new lock yesterday.
Installation uses strongly favor the “fitted” past form.
The jacket fitted well.
“Fitted” is a standard past form for size.
The jacket fit well when I tried it on.
Past “fit” is also common in US English for the size/suitability sense.
Further guidance
Core difference
“Fitted” is standard as the past tense and participle; US English also commonly uses “fit” in size/suitability senses. Installation uses strongly favor “fitted.”
Usage Boundary
Choose the form that matches tense, participle role, meaning, region, or lexicalized use; do not treat the pair as freely interchangeable in every sentence.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Fit — Cambridge Dictionary (opens in a new tab)Cambridge Dictionary · Cambridge lists fitted as the general past form and fit as an additional US past form; fitted also remains standard in installation senses.