SAAG Calculator (serum-ascites albumin gradient)

Understanding the SAAG calculator — concept and principle

The serum-ascites albumin gradient (SAAG) helps find the cause of ascites, fluid in the abdomen. It subtracts the albumin in the ascitic fluid from the albumin in the blood, both taken on the same day, and shows whether the fluid is likely due to portal hypertension.

Serum minus ascites: with the default inputs the result is SAAG 2.0 (≥ 1.1 → portal hypertension).

How it is calculated

SAAG = serum albumin − ascitic fluid albumin

Enter both in g/dL or both in g/L; the result is shown in both units (1 g/dL = 10 g/L).
1.1 g/dL (11 g/L) or more: high gradient, portal hypertension.
Below 1.1 g/dL: low gradient, other causes.

The principle

In portal hypertension, high pressure in the liver's blood vessels pushes fluid out with little protein, so albumin in the ascites stays much lower than in blood and the gradient is large. When ascites comes from inflamed or invaded peritoneum, as in cancer or tuberculosis, protein-rich fluid leaks out and the gap between blood and fluid albumin is small. The gradient reflects pressure, not just leakiness, which is why it outperformed the older exudate/transudate approach.

Worked example

Default inputs: serum albumin 2.9 g/dL, ascitic albumin 0.9 g/dL.

SAAG = 2.9 − 0.9 = 2 g/dL = 20 g/L.
2.0 ≥ 1.1 → High (1.1 g/dL or more).
Usually points to Portal hypertension (e.g. cirrhosis, heart failure).

Each point is the calculator re-run with only “Serum albumin” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Serum albumin	SAAG (g/dL)
0.725	-0.18
1.45	0.55
2.17	1.27
2.9	2
3.62	2.73
4.35	3.45
5.8	4.9

How to read the result

Where does your result fall?

A high gradient has a diagnostic accuracy of about 97% for portal hypertension, most often from cirrhosis, but heart failure and Budd-Chiari syndrome also give high values. A low gradient points to peritoneal cancer, tuberculosis, pancreatitis or nephrotic syndrome. Mixed causes, such as cirrhosis plus cancer, can be misclassified, so the result is read with ascitic protein, cell count, culture and cytology.

Common mistakes

Using serum and ascitic samples from different days.
Computing a ratio instead of a difference.
Mixing g/dL and g/L between the two values.

Keep in mind: This is a decision aid for clinicians, not a diagnosis. New or worsening abdominal swelling needs medical assessment.

Frequently asked questions

What does a SAAG of 1.1 or more mean?

The ascites is most likely due to portal hypertension.

Does treatment with diuretics change the SAAG?

The gradient generally remains useful, though both albumin values may change.

How does ascitic protein help?

In a high-gradient ascites, high protein suggests heart failure rather than cirrhosis.

Sources: Asian Pacific Association for the Study of the Liver (APASL), clinical practice guidance on the management of ascites, Hepatol Int 2023 · Runyon BA, Montano AA, Akriviadis EA, et al., "The serum-ascites albumin gradient is superior to the exudate-transudate concept in the differential diagnosis of ascites", Ann Intern Med 1992;117(3):215–220

Checked 9 Nov 2026. Asian Pacific Association for the Study of the Liver (APASL), clinical practice guidance on the management of ascites, Hepatology International 2023 (doi:10.1007/s12072-023-10536-7): SAAG ≥ 1.1 g/dL for portal hypertensive ascites, diagnostic accuracy 97%, and its limits in mixed ascites.

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