Saturate – Effective O₂

At 10,000 feet, every breath you take delivers about 30% less oxygen than at sea level. Saturate turns your Apple Watch into a live oxygen meter for the air around you — so you can see exactly what you're breathing while you climb, ski, hike, or fly. Using the barometer on your wrist, Saturate measures the actual air pressure around you and converts it into "effective oxygen": the sea-level equivalent of what each breath delivers right now. At the beach, that's 20.9%. In Denver, about 17%. On a 14,000-foot summit, closer to 12%. WHAT YOU SEE • Effective oxygen % — the headline number on a color-coded ring • % of sea-level oxygen — 100% at the beach, falling as you climb • Six altitude zones, from Low (green) to Ultra (indigo) • A live altitude scale from sea level to 29,000 ft, with a marker for where you stand • Your current altitude, air pressure, and nearby place name • A trend arrow that shows whether your air is getting richer or thinner ON YOUR WATCH FACE Three complication styles for any face: a rectangular overview with oxygen, altitude, and % of sea level at a glance, plus focused Effective O₂ and % of Sea Level gauges for circular, corner, and inline slots. They quietly keep themselves fresh through the day. BUILT FOR THE WRIST • Watch-only — nothing to install on your iPhone, nothing extra to carry up the mountain • Steady by design — readings are smoothed so the number locks in instead of flickering • Feet or meters, with an optional extra decimal of precision • Falls back to GPS altitude on watches without a barometer PRIVATE BY DESIGN No account. No ads. No analytics. No developer servers. Every reading is computed on your watch, from your watch. If you enable location, Apple's geocoding service may be used to show a nearby place name — that's it. GREAT FOR • Hikers, climbers, mountaineers, and trail runners • Skiers and snowboarders • Altitude training and acclimatization awareness • Travelers to high-altitude cities • Frequent flyers — watch the cabin "climb" to 7,000 feet • Anyone curious about the invisible air around them NOT A MEDICAL DEVICE Saturate measures the surrounding air — not your blood oxygen (SpO₂). It does not diagnose, treat, or provide medical advice. Always follow proper acclimatization guidance at altitude.