INR Calculator

Free calculate INR (International Normalized Ratio) from PT and ISI. This is an educational tool only - always consult a healthcare provider.

Laboratory Values

Typical ISI: 1.0-1.2 (check with your lab)

Results

Enter lab values to calculate INR

About INR

  • • Normal: 0.9-1.1
  • • Warfarin target: 2.0-3.0 (most indications)
  • • Mechanical valve: 2.5-3.5
  • • INR = (PT / Control PT)^ISI