Newcastle-Ottawa Scale Calculator for Cohort and Case-Control Studies
Score observational studies with the Newcastle-Ottawa Scale star system: selection (up to 4 stars), comparability (up to 2) and outcome or exposure (up to 3), for a total out of 9.
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Study design
Summary
Study
Selection
Comparability
Outcome
Total
Example cohort 1
★★★★
★★
★★★
9/9
Example cohort 2
★★★☆
★☆
★★☆
6/9
Example cohort 3
☆☆☆☆
☆☆
☆☆☆
0/9
The scale gives at most one star per item, except comparability (up to two). It does not define cut-offs for good, fair or poor quality, so state any thresholds you use in your protocol.
How to Use the Newcastle-Ottawa Scale Calculator
1
Choose the design
Cohort or case-control studies.
2
Answer each item
Stars are awarded automatically.
3
Download the table
CSV or copy the scores into your review.
How the Newcastle-Ottawa Scale works
The Newcastle-Ottawa Scale (NOS) assesses the quality of non-randomised studies in meta-analyses. Studies earn stars in three categories: selection of the study groups, comparability of the groups, and ascertainment of the outcome (cohort studies) or exposure (case-control studies).
A study can earn at most one star for each selection and outcome or exposure item, and up to two for comparability, so the maximum is nine stars. The scale itself does not define cut-offs for good, fair or poor quality.
Can the Newcastle-Ottawa Scale be used for cross-sectional studies?
The official scale covers cohort and case-control studies only. If you use an adapted version for another design, cite the adaptation and describe it in your methods.
What NOS score counts as high quality?
The scale does not set one. Pre-specify any threshold in your protocol and report the domain scores, not just the total.
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