What this calculator does
Physiological stress tends to push neutrophils up and lymphocytes down at the same time. Dividing one by the other amplifies both movements into a single number, which is why the ratio has attracted so much research interest.
It is nonspecific by nature. A healthy adult typically sits between 1 and 2, and values above about 3 have been studied as a marker of stress or inflammation across a very wide range of conditions, which is both its appeal and its weakness.
The formula
Divide the absolute neutrophil count by the absolute lymphocyte count. Both come from a routine differential, in cells per microlitre.
| Term | Meaning |
|---|---|
| NLR | Neutrophil-to-lymphocyte ratio, a dimensionless number. |
| Absolute counts | Cells per microlitre rather than percentages, which is what the ratio requires. |
| Nonspecific marker | A signal that something is happening, without indicating what. |
The inputs explained
| Field | What to enter |
|---|---|
| Absolute neutrophil count (cells/µL) | Absolute neutrophil count in cells per microlitre. |
| Absolute lymphocyte count (cells/µL) | Absolute lymphocyte count in cells per microlitre, from the same differential. |
When to use it
Assessing physiological stress
The ratio rises with infection, trauma, surgery and severe illness generally.
Following a trend
A rising ratio over successive counts is more informative than any single value.
Reading research literature
NLR appears as a prognostic marker across a very wide range of studies.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How does the neutrophil count move the ratio?
Three neutrophil counts against the same lymphocyte count.
| Neutrophil count | NLR | Reading |
|---|---|---|
| 2,000 cells/µL | 1.00 | Within the typical range |
| 4,000 cells/µL | 2.00 | Within the typical range |
| 9,000 cells/µL | 4.50 | Elevated: often studied as a marker of physiological stress or inflammation |
Questions
What does a raised ratio actually indicate?
That the body is under some form of physiological stress. It does not distinguish between infection, inflammation, trauma, malignancy or severe stress of any other kind, which limits what it can be used for on its own.
Why has it been studied so widely?
Because it costs nothing, being derived from a test already performed, and because it correlates with outcomes across many conditions. That breadth is also why it rarely changes management in any specific one.
Does it need absolute counts?
Yes. Using percentages instead gives a different number, since percentages are shares of a white cell count that is itself changing. The absolute figures are what the published thresholds refer to.
Is there an agreed cut-off?
No. Studies use thresholds anywhere from 2 to 5 depending on the population and outcome, which is a good indication that no single value carries general meaning.
For the neutrophil count itself, see the absolute neutrophil count calculator. For red cell indices, see the MCH and MCHC calculator.