ECG Heart Rate Calculator

ECG Heart Rate Formula

Worked Example

An R–R interval of 800 ms with a QT of 400 ms:

1. HR = 60 ÷ RR = 60 ÷ 0.8 s
2. HR = 75 beats per minute

QTc (Bazett) QT/√RR: 447.2135955 ms · QTc (Fridericia) QT/∛RR: 430.886938 ms

GATE tip

ECG amplifiers need a CMRR above about 80 dB and a bandwidth of 0.05–100 Hz (diagnostic) or 0.5–40 Hz (monitoring); a 50/60 Hz notch tackles mains interference.

More Bioinstrumentation and Physiology Calculators

• Cardiac Output Calculator

  CO = SV × HR, CO = VO₂ / (CaO₂ − CvO₂)

  cardiac index CI = CO / BSA; BSA (Mosteller) = √(height cm × weight kg / 3600)

  Example: A stroke volume of 70 mL at 72 beats per minute (170 cm, 70 kg): Cardiac output CO = 5.04 L/min.

  Open the cardiac output calculator →

• Mean Arterial Pressure Calculator

  MAP ≈ DBP + (SBP − DBP)/3

  pulse pressure PP = SBP − DBP; the 1/3 reflects that diastole lasts about twice as long as systole

  Example: A blood pressure of 120/80 mmHg: Mean arterial pressure = 93.3333 mmHg.

  Open the mean arterial pressure calculator →

• Poiseuille Flow Calculator

  Q = π r⁴ ΔP / (8 μ L)

  resistance R = 8μL/(πr⁴); valid for steady laminar flow of a Newtonian fluid

  Example: Blood (3.5 mPa·s) through a 2 mm radius, 10 cm vessel with 100 Pa pressure difference: Flow rate Q = 1.7952 mL/s.

  Open the poiseuille flow calculator →

• Nernst Equation Calculator

  E = (RT/zF) ln([C]ₒᵤₜ/[C]ᵢₙ)

  R = 8.314 J/(mol·K), F = 96,485 C/mol, z the ion’s valence; 61.5 mV per decade at 37 °C for z = 1

  Example: Potassium with 5 mM outside and 140 mM inside the cell at 37 °C: Equilibrium potential E = -89.0587 mV.

  Open the nernst equation calculator →

Frequently asked questions

Sources

• The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .

Last reviewed: 2026-10-15. Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.