Pediatrics 2004; 114(2 Suppl 4th Report): 555-76. Rosner B, Cook N, Portman R, Daniels S, Falkner B. Determination of blood pressure percentiles in normal-weight children: some methodological issues.

Blood pressure is measured in two numbers: systolic and diastolic. The top number is the systolic blood pressure, which measures the pressure caused by the heart contracting and squeezing out blood.