Canonical: https://echosuite.app/guides/ra-size/

# Right atrial size calculator and measurement guide

Explore right atrial size measurements, acquisition guidance and the reference context supplied with the tool.

Created by [Mohammed Kamareddine, MD](https://echosuite.app/about/) · [Sources & educational scope](https://echosuite.app/about/)

[Open interactive calculator →](https://echosuite.app/calculators/#ra-size)

## Method

Grade the selected RA measure against the 2025 ASE method-specific table; volume methods index to BSA

Use the measurement units shown below. Some fields apply only to a selected method or condition; follow the interactive tool’s method choices. The interactive tool keeps missing measurements incomplete and provides its method-specific results and reference context.

## Measurements and acquisition

### Measure

Enter the measured value in the displayed unit

- RA volume index · method of disks
- RA volume index · area–length
- RA major dimension
- RA minor dimension
- RA end-systolic area
- Confirm the variable matches the selected formula.
- Use the unit displayed beside the field.
- Keep measurements from the same representative hemodynamic state.

### RA volume  mL

Enter the measured value in the displayed unit

- Confirm the variable matches the selected formula.
- Use the unit displayed beside the field.
- Keep measurements from the same representative hemodynamic state.

### Body surface area  m²

Record the units, date and measurement source

- Use measured height and weight where feasible. Record the units, date and whether a value was reported or estimated.
- Fluid status and weight changes affect BSA. Document any substituted weight; do not silently replace measured weight with ideal or dry weight.
- Use the unit named by the field. BSA is in m²; height and weight can be converted in the Body surface area calculator. Keep the formula with serial indexed results.

### RA major dimension  cm

2D echo · inner-edge measurement

- Use the specified view and cardiac phase.
- Align the calipers perpendicular to the structure’s long axis.
- Measure inner edge to inner edge and avoid oblique foreshortening.

### RA minor dimension  cm

2D echo · inner-edge measurement

- Use the specified view and cardiac phase.
- Align the calipers perpendicular to the structure’s long axis.
- Measure inner edge to inner edge and avoid oblique foreshortening.

### RA end-systolic area  cm²

Enter the measured value in the displayed unit

- Confirm the variable matches the selected formula.
- Use the unit displayed beside the field.
- Keep measurements from the same representative hemodynamic state.

### Entered value

Enter the measured value in the displayed unit

- Confirm the variable matches the selected formula.
- Use the unit displayed beside the field.
- Keep measurements from the same representative hemodynamic state.

## Sources and method context

American Society of Echocardiography · 2025 · Guidelines for the Echocardiographic Assessment of the Right Heart in Adults and Special Considerations in Pulmonary Hypertension · RA acquisition, methods and Table 1 partitions: 2025 right-heart guideline pp. 2, 4, 6, and 10.

[Primary reference](https://www.asecho.org/wp-content/uploads/2026/08/ASE-Right-Heart-Guidelines-May-2025.pdf)

- RA measurement methods · ASE 2025 right-heart guideline · pp. 2, 6, 10

Dedicated RA-focused A4C. Single-plane method of disks is the preferred 2D volume when indexed to BSA; area–length is a different method and is not interchangeable. Linear dimensions and area are supporting measures.

- RA reference partitions · ASE 2025 right-heart guideline · Table 1 p. 4; key points p. 2

Method-specific RA dimension, area, MOD-volume, and area–length volume partitions. Area–length is a different table from method of disks.

Catalogue review status: Source mapped · clinical sign-off pending

These pages describe the educational tool. Interpret measurements with the complete clinical context and the method’s acquisition limitations.

## Keep exploring

- [Apical four chamber acquisition guide](https://echosuite.app/guides/views/apical-four-chamber/) · [Open in Probe Lab](https://echosuite.app/#a4c)
- [Right atrial pressure assessment: IVC and hepatic vein flow](https://echosuite.app/guides/rap/)
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- [Right-heart echocardiography: views, measurements and calculators](https://echosuite.app/learn/right-heart-echo/)

[All echo guides](https://echosuite.app/guides/) · [Learning paths](https://echosuite.app/learn/)