The Oxygen Level Calculator interprets pulse oximeter SpO₂ readings and optional pulse rate. It classifies oxygenation as Normal (≥95%), Low (90–94% — mild hypoxemia), Moderate (85–89%), or Critical (<85%) and gives clear safety guidance. If you also enter Hemoglobin (g/dL) and PaO₂ (mmHg), it estimates arterial oxygen content (CaO₂) using the standard formula CaO₂ = (Hb × 1.34 × SaO₂) + (0.0031 × PaO₂), where SaO₂ ≈ SpO₂/100 (this is an approximation).