Enter the ultrasound score, menopausal status, and serum CA-125 level into the calculator to determine the RMI.

RMI Calculator

RMI I
RMI 4 (with size)

Tick ultrasound findings, pick menopausal status, enter CA-125.

Ultrasound findings
Multilocular cysts
Solid areas
Bilateral lesions
Ascites
Intra-abdominal metastases
U/mL

Medical note: For informational/educational use only. Not medical advice and not a diagnosis. RMI (and CA‑125) are interpreted by clinicians alongside imaging, symptoms, and exam findings; CA‑125 can be elevated for many non‑cancer conditions. Referral thresholds and definitions (including menopausal status) vary by guideline and setting—use the classification and cutoffs provided by your clinician. Privacy: If enabled, this tool can save your last tab/results in your browser; disable “Remember” and use Reset on shared devices.

Related Calculators

RMI I (Risk of Malignancy Index) Formula

The following formula is commonly used to calculate RMI I (one of several published RMI versions):

RMI = U * M * CA125

Variables:

  • RMI is the Risk of Malignancy Index
  • U is the ultrasound score (for RMI I, U = 0 if no suspicious ultrasound features are present, U = 1 if 1 feature is present, and U = 3 if 2 or more features are present)
  • M is the menopausal status (for RMI I, 1 for premenopausal and 3 for postmenopausal)
  • CA125 is the serum CA-125 level (U/mL)

To calculate RMI I, multiply the ultrasound score (U) by the menopausal status (M), then multiply the result by the serum CA-125 level.

RMI IV (RMI 4) Formula & Variable Definitions

Another published variant is RMI IV (often shown as “RMI 4”), which includes tumor size (S) in addition to ultrasound score (U), menopausal status (M), and CA-125:

RMI4 = U * M * S * CA125

Commonly used component scoring for RMI 4:

  • U (ultrasound score): U = 1 if 0–1 ultrasound features are present; U = 4 if 2 or more features are present
  • M (menopausal status): M = 1 (premenopausal) or M = 4 (postmenopausal)
  • S (size): S = 1 for < 7 cm; S = 2 for ≥ 7 cm (largest diameter)
  • CA125: serum CA-125 level (U/mL)

Some clinical pathways use a referral cutoff of 450 for RMI 4, but thresholds and scoring details can vary by guideline and setting—check the guidance used by your local health system or specialist team.

What is a RMI (Risk Of Malignancy Index)?

The Risk of Malignancy Index (RMI) is a scoring system used in gynecology to help estimate the risk of ovarian cancer in women presenting with an adnexal (ovarian) cyst or mass. It combines diagnostic components such as an ultrasound-based score, menopausal status, and the serum CA-125 blood biomarker. Multiple versions of the RMI exist (e.g., RMI I and RMI IV), and higher scores generally indicate higher risk.

How to Calculate RMI (Risk Of Malignancy Index)?

The following steps outline how to calculate the Risk of Malignancy Index (RMI) using the given formula:

  1. First, determine the ultrasound score (U). For RMI I, U is based on the number of suspicious ultrasound features present (multilocular cysts, solid areas, bilateral lesions, ascites, or intra-abdominal metastases): U = 0 (0 features), U = 1 (1 feature), U = 3 (2 or more features).
  2. Next, determine the menopausal status (M). Assign a value of 1 for premenopausal or 3 for postmenopausal (RMI I).
  3. Next, determine the serum CA-125 level (CA125) in U/mL.
  4. Next, use the formula RMI = U * M * CA125 to calculate the Risk of Malignancy Index (RMI I).
  5. Finally, insert the values of U, M, and CA125 into the formula and calculate the RMI.

Example Problem:

Use the following variables as an example problem to test your knowledge:

ultrasound score (U) = 3

menopausal status (M) = 3

serum CA-125 level (CA125) = 120 U/mL