E6B Calc, a digital E6B flight computer for iPhone and iPad

What can you work out with it?

The home screen, E6B, groups the calculators in the rough order a pilot reaches for them before and during a flight, not alphabetically.

• Flight: Density Altitude, True Airspeed (with Mach), True Altitude for cold days, Wind Triangle, runway Crosswind with gusts, and the Analogue E6B wind wheel.
• Planning: Time · Speed · Distance, Fuel with reserve, and PNR & Equal Time Point.
• Performance: climb and descent gradients with an obstacle check, turn rate and radius, and engine-out glide range.
• Navigation: great-circle distance, Magnetic & Compass (true to magnetic to compass) and Holding Entry.
• Weather: Cloud Base & Freezing Level and the METAR & TAF Decoder.
• Weight & Balance with your own aircraft profile, CG envelope chart and limits check.
• Time and Tools: Zulu and local clocks, sun and twilight times, a Flight Timer that shows on the Lock Screen, a Countdown, Conversions and History.

Quick start: density altitude in four steps

1. Open E6B and tap Density Altitude under Flight.
2. Type the Field elevation in feet with the app's own keypad, for example 5000.
3. Check the Altimeter setting (it starts at standard pressure) and type the Outside air temperature, for example 30 °C.
4. Read Pressure altitude 5,000 ft, Density altitude 7,800 ft and ISA deviation +24.9 °C. The calculation is saved to History when you leave the screen.

The keypad has large keys and a plus/minus key for negative temperatures and variation. It also has Next field and Done, so the iOS keyboard almost never pops up. If it disappears after rotating the iPad mid-entry, tap Show keypad and it comes straight back.

Free, with an optional E6B Pro

The app is free and shows no ads. Every calculator, conversion, clock, timer and the keypad are free and unlimited. E6B Pro is one payment, not a subscription. It adds:

• unlimited METAR and TAF decoding (3 free decoding visits first);
• unlimited use of the Analogue E6B wheel (3 free opens first);
• unlimited Exam mode sessions (2 free);
• more than one aircraft in Weight & Balance and your whole History visible (free shows the 10 newest);
• the Crosswind and Density Altitude widgets. The Zulu Clock widget is free.

Offline, no account, no permissions

All the maths runs on the device. That matters more than it sounds: it works the same with the phone in airplane mode at 9,000 ft. The METAR decoder is offline too, because you paste the report in rather than fetching it. No sign-up, no permissions asked — not location, not camera, not tracking. If your device is signed in to iCloud, calculations and aircraft sync to your iPhone, iPad and the Apple Watch app. Off iCloud, they just stay on the one device.

Units for pilots everywhere

Settings > Units of measurement covers the altimeter setting (inHg or hPa), speed (kt, km/h or mph), distance (nm, km or sm), temperature (°C or °F) and fuel (US gallons, litres or imperial gallons). Altitude stays in feet and heading in degrees regardless, same as the cockpit.

Apple Watch and widgets

The companion Apple Watch app works out runway crosswind, density altitude and time-distance-speed on the watch itself, no phone nearby required. On the iPhone, Home Screen and Lock Screen widgets read a Home Field observation you type in yourself — they never go fetch weather, which is worth knowing before you trust one at a glance. No watch complications, for now.

What it does not do

• It does not download METARs, TAFs, winds aloft or NOTAMs, and it has no airport database or GPS.
• True Airspeed starts from calibrated airspeed; there is no IAS table for your aircraft.
• Density altitude assumes dry air: humidity is not an input.
• No aircraft library: you type your own weight and balance data.
• No Mac or Android app, and no export or printing of results.