Centor Score Calculator

Calculate the Centor or McIsaac score for streptococcal pharyngitis likelihood.

About Centor Score Calculator

Even the highest score corresponds to only about a 55 per cent probability of streptococcal infection, which is why the score guides testing rather than replacing it. Most sore throats are viral regardless of score. The score exists primarily to reduce unnecessary antibiotic prescribing, since the majority of sore throats resolve without treatment.

Formula

Centor Score

Centor sums four clinical criteria; McIsaac adds an age modifier of plus or minus one

Centor: Exudate, tender nodes, fever history and absence of cough
McIsaac modification: Adds one point under 15 and subtracts one at 45 or over

Worked example

With the default values below, Centor Score Calculator returns McIsaac Score of 4. Change any input above and every figure here is recalculated in your browser.

Inputs used

Tonsillar exudateone of Yes, No: Yes
Tender anterior cervical nodesone of Yes, No: Yes
History of fever above 38 Celsiusone of Yes, No: Yes
Cough absentone of Yes, No: Yes
Ageaccepts 1–110 years: 22 years

Results

McIsaac Score: 4 /5
Centor Score: 4 /4
Published Probability of Streptococcal Infection: 55.0%
Age Modifier Applied: 0
Interpretation: Higher probability — testing or empirical treatment may be considered per local protocol

Step by step

1Values used
2Centor Score
3McIsaac Score= 4 /5
4Centor Score= 4 /4
5Published Probability of Streptococcal Infection= 55.0
6Age Modifier Applied= 0
7Interpretation= Higher probability — testing or empirical treatment may be considered per local protocol

Assumptions and limits

The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
This reproduces a published formula for educational and reference use only. It is not a diagnostic tool, does not account for individual clinical context, and must not be used to make or change treatment decisions. Clinical assessment by a qualified healthcare professional is always required. Antibiotic decisions must be made by a prescriber following local guidance and resistance patterns. Seek urgent care for difficulty swallowing or breathing, drooling, or a severe unilateral sore throat.
This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

This reproduces a published formula for educational and reference use only. It is not a diagnostic tool, does not account for individual clinical context, and must not be used to make or change treatment decisions. Clinical assessment by a qualified healthcare professional is always required. Antibiotic decisions must be made by a prescriber following local guidance and resistance patterns. Seek urgent care for difficulty swallowing or breathing, drooling, or a severe unilateral sore throat.

Frequently Asked Questions

How is Centor Score calculated?

Centor sums four clinical criteria; McIsaac adds an age modifier of plus or minus one Even the highest score corresponds to only about a 55 per cent probability of streptococcal infection, which is why the score guides testing rather than replacing it. Most sore throats are viral regardless of score.

Why does Centor Score matter?

The score exists primarily to reduce unnecessary antibiotic prescribing, since the majority of sore throats resolve without treatment.

What values do I need to enter?

This calculator takes 5 inputs: Tonsillar exudate, Tender anterior cervical nodes, History of fever above 38 Celsius, Cough absent, Age. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.