MAGENT

Neutrophil lymphocyte ratio (NLR): formula and examples

The neutrophil lymphocyte ratio (NLR) is the neutrophil percentage divided by the lymphocyte percentage from a white blood cell differential. Neutrophils tend to rise and lymphocytes tend to fall during physical stress and inflammation, so the ratio moves more than either count alone. Magent's NLR calculator does the division and returns the ratio to two decimal places.

Not a medical device. Not a diagnosis or dosing recommendation.

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What is the neutrophil lymphocyte ratio?

Zahorec described the ratio in 2001 in critically ill patients, as a quick marker of systemic inflammation and stress that could be read from a routine blood count. Because it needs no extra test, it has since been studied in many settings.

The calculator uses the relative counts, as percentages of all white cells. Dividing the two percentages gives the same answer as dividing the two absolute counts from the same sample, since both share the same total.

The calculator returns the ratio and applies no cut-offs.

The neutrophil lymphocyte ratio formula

NLR = neutrophil % / lymphocyte %

both as percentages of white blood cells
result rounded to 2 decimal places

Exact expression the calculator uses:

nlr = neutrophil_percent / lymphocyte_percent

Inputs

InputMeaningRange
neutrophil_percentNeutrophils as a percentage of white cells0.1 to 99
lymphocyte_percentLymphocytes as a percentage of white cells0.1 to 99

The lymphocyte percentage must be above 0, because it's the divisor. Values outside the range return an error.

How the calculation works

  1. Read the differential. Take the neutrophil and lymphocyte percentages from the same blood count.
  2. Divide. Neutrophil percentage ÷ lymphocyte percentage.
  3. Round. The result is given to two decimal places.

A higher ratio means relatively more neutrophils and fewer lymphocytes.

Worked examples

These use Magent's own expected values for the calculator.

Example 1: neutrophils 70%, lymphocytes 20%

  1. 70 ÷ 20.
  2. NLR 3.5.

Example 2: equal percentages

  1. Neutrophils 50%, lymphocytes 50%.
  2. NLR 1.0.

Example 3: the extremes of the input range

  1. Neutrophils 99%, lymphocytes 0.1%.
  2. NLR 990.0. A very small divisor gives a very large ratio.

History of the neutrophil lymphocyte ratio

Zahorec R published the ratio in Bratislavske Lekarske Listy in 2001, in "Ratio of neutrophil to lymphocyte counts--rapid and simple parameter of systemic inflammation and stress in critically ill". Later studies looked at it in other settings, and some proposed cut-offs. Those cut-offs vary between studies and aren't part of this calculator.

When it's used

The ratio is worked out from a routine full blood count with differential, when a simple marker of inflammation or stress is wanted alongside the clinical picture.

Where it's used

Intensive care, emergency departments, hospital wards and research.

Who uses it

Intensivists, emergency physicians, internists and researchers. The calculator does the division.

Limits of the calculation

  • It isn't specific. Infection, surgery, trauma, steroids, stress and blood disorders can all change it.
  • It changes quickly, so a single value reflects one moment.
  • The calculator applies no cut-offs and doesn't identify sepsis, cancer or any other condition.
  • Rounding to two decimals hides very small differences.
  • This page doesn't say what a result means for a particular person.

Clinical decisions belong to a qualified clinician who knows the patient.

  • ANC gives the absolute neutrophil count, not a ratio.
  • SIRS counts clinical signs of a systemic inflammatory response, including the white cell count.

Glossary

  • Differential: the breakdown of white blood cells by type.
  • Neutrophils: white cells that respond early to infection and stress.
  • Lymphocytes: white cells involved in immune memory and regulation.
  • Relative count: a cell type as a percentage of all white cells.

Common mistakes

  • Mixing percentages and absolute counts. Use percentages for both, as the calculator expects.
  • Taking the two values from different samples. Both should come from the same blood count.
  • Entering 0 for lymphocytes. The divisor must be above 0.
  • Applying a cut-off from one study as a rule. Proposed cut-offs differ, and the calculator uses none.

Source

Zahorec R. Ratio of neutrophil to lymphocyte counts--rapid and simple parameter of systemic inflammation and stress in critically ill. Bratisl Lek Listy. 2001;102(1):5-14. DOI: 10.1007/bf03656390. PMID: 11723675

Frequently asked questions

How do you calculate the neutrophil lymphocyte ratio?

Divide the neutrophil percentage by the lymphocyte percentage from the same blood count.

Does the calculator say what a normal NLR is?

No. It returns the ratio. Proposed cut-offs vary between studies, and none is applied.

Can I use absolute counts instead?

From the same sample, the ratio of absolute counts equals the ratio of percentages. This calculator takes percentages.

Is a high NLR a sign of sepsis?

The ratio can rise with infection and many other conditions. It doesn't identify sepsis on its own.

Who first described the NLR?

Zahorec, in 2001, in critically ill patients.