RA is more difficult to estimate than LA. There are only a few echocardiographic measurements. In many cases, we look at the AP4CH to the ratio LA / RA: LA is normally slightly larger.
RA size
| MALE | FEMALE |
| Mean ± SD | Mean ± SD |
RA minor axis diameter (cm/m²) | 1.9 ± 0.3 | 1.9 ± 0.3 |
RA major axis diameter (cm/m²) | 2.5 ± 0.3 | 2.4 ± 0.3 |
(2D echo) RA volume (mL/m²) | 21 ± 6 | 25 ± 7 |

RA pressure
Inferior Vena Cava size | Estimation RA pressure |
Normal <21mm, collaps >50% | 3 mmHg (range 0–5 mmHg) |
Borderline <21mm, collaps <50% | 8 mmHg (range 5–10 mmHg) |
Borderline >21mm, collaps >50% | 8 mmHg (range 5–10 mmHg) |
Dilated >21mm, collaps < 50% | 15 mmHg (range 10- 20 mmHg) |

References
Eur Heart J Cardiovasc Imaging. 2015 Mar;16(3):233-70