Systemic Immune-Inflammation Index (SII) Calculator

Calculate SII from platelets, neutrophils and lymphocytes — and see why no single cut-off applies across conditions.

Last updated 31 Aug 2026

Systemic Immune-Inflammation Index (SII)

Platelets × ANC ÷ ALC

Platelets (×10⁹/L)

Absolute neutrophils (×10⁹/L)

Absolute lymphocytes (×10⁹/L)

1655SIIExample

Platelets 280, ANC 6.5, ALC 1.1 (all ×10⁹/L)

Formula

SII = platelets × absolute neutrophils ÷ absolute lymphocytes

platelets: ×10⁹/L
ANC: ×10⁹/L — absolute neutrophil count
ALC: ×10⁹/L — absolute lymphocyte count

Worked example

Platelets 280, ANC 6.5, ALC 1.1 (all ×10⁹/L)
280 × 6.5 = 1820
1820 ÷ 1.1 = 1655
Above 900 — higher range

Published SII cut-offs vary by cohort

There is no universal SII cut-off. The bands used in this calculator are indicative only, chosen to span the range reported in the general literature.
Cohort	Reported 'high' cut-off
Hepatocellular carcinoma	≈ 330
Gastric cancer	≈ 660
Mixed solid tumours, general population studies	≈ 900 – 1200+

Combining three cell lines — and why there is no single cut-off

The systemic immune-inflammation index folds all three cell lines that NLR and PLR use separately into one number: platelets and neutrophils in the numerator, lymphocytes in the denominator. The logic is that if platelet and neutrophil rises and a lymphocyte fall each carry some prognostic signal, multiplying rather than choosing between them should carry more information than any one ratio alone, and in several cancer cohorts it has outperformed NLR and PLR individually.

What it has not produced is a stable threshold. Published cut-offs for a ‘high’ SII range from roughly 330 in some hepatocellular carcinoma cohorts to over 1200 in others, depending on the cancer type, the stage mix of the population studied, and the statistical method used to derive the cut-point. A value flagged as high risk in one paper would be unremarkable in another.

There is no universal SII cut-off, and the bands shown here are indicative only, chosen to span the range reported across the general literature rather than validated for any specific condition. SII is best used, like NLR and PLR, as a supporting marker of inflammatory burden rather than a number with an agreed clinical action attached to it.

Frequently asked questions

What is the systemic immune-inflammation index?

A single number combining platelets, neutrophils and lymphocytes — platelets times neutrophils, divided by lymphocytes — intended to capture more prognostic information than any one cell-line ratio alone.

What counts as a high SII?

There is no agreed threshold. Published cut-offs range from about 330 to over 1200 depending on the cancer type and population studied, so a single number should be read with real caution.

Is SII better than NLR or PLR?

In some cohorts it has outperformed either ratio alone, but the evidence is observational and cut-offs are not standardised, so it has not replaced them in guidelines.

Should SII change management on its own?

No. It is a supporting marker of inflammatory burden, not a validated decision threshold, and should be interpreted alongside the clinical picture and more specific tests.

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References

Hu B et al. Systemic immune-inflammation index predicts prognosis of patients after curative resection for hepatocellular carcinoma. Clin Cancer Res. 2014;20(23):6212–22.
Fest J et al. The systemic immune-inflammation index is associated with an increased risk of incident cancer — a population-based cohort study. Int J Cancer. 2020;146(3):692–98.