This hemodynamic study documented the accuracy and precision of six empirical formulas relating mean (mPAP), systolic (sPAP), and diastolic (dPAP) pulmonary artery pressures in children with congenital heart disease. Fluid-filled PAPs of 61 children (age, 26 ± 40 months) were analyzed over an mPAP range of 7 to 74 mmHg. All formulas were accurate (mean bias, −2 to 1 mmHg). The three formulas relying on sPAP and dPAP were dPAP + 1/3 (sPAP – dPAP), dPAP + 0.41 (sPAP – dPAP), and sqrt of (sPAP × dPAP). They were precise (bias standard deviation [SD], 3 mmHg), with approximately 90% of patients exhibiting biases of less than 5 mmHg. The three formulas relying on sPAP alone all assumed that mPAP approached two-thirds of sPAP according to slightly different mathematical equations. They were less precise (bias SD, 5–6 mmHg), with biases greater than 7 mmHg for 10% to 16% patients. Accurate estimates of mPAP were obtained from sPAP alone, and this could be valuable for cross-checking the self-consistency of the pressure database obtained in the echo-Doppler laboratory. For cases that had reliable dPAP estimates available, empirical formulas relying on both sPAP and dPAP were more precise and thus must be preferred.