E6B Flight Computer
Solve the wind triangle, time-speed-distance, and fuel, plus the unit conversions every pilot needs. Runs entirely in your browser.
What an E6B does
The E6B is the circular slide rule every pilot learns for the private certificate. One side is a wind face that solves the wind triangle graphically; the other is a rotating scale for time, speed, distance, fuel, and conversions. This page does the same four jobs with exact arithmetic instead of a pencil dot: the wind triangle (true heading and ground speed), time and distance at a ground speed, fuel required with a reserve, and the unit conversions that turn up in every flight plan. Nothing is sent to a server, so it works on the ramp with no signal.
How the E6B wind triangle works
The wind triangle finds the heading you must fly and the ground speed you'll make good when wind pushes you off your course. Given your true course, true airspeed, and the wind (direction it blows from and speed), the calculator computes the wind correction angle (WCA), your true heading, and ground speed:
- WCA = arcsin( (wind speed ÷ TAS) × sin(wind angle) )
- True heading = true course + WCA
- Ground speed = TAS × cos(WCA) − wind speed × cos(wind angle)
The wind angle is the difference between where the wind is from and your course. A wind from the right gives a positive WCA (turn right, into it); a wind from the left gives a negative one. A direct headwind or tailwind has a wind angle of 0° or 180°, so the WCA is zero and the whole wind speed comes off, or goes onto, your ground speed.
Worked example
True course 090°, true airspeed 110 kt, winds aloft 040° at 20 kt. The wind is 50° left of the nose.
- Wind angle = 040 − 090 = −50°. sin(−50°) = −0.766.
- WCA = arcsin( (20 ÷ 110) × −0.766 ) = arcsin(−0.139) = −8°. The wind is from the left, so you crab 8° left.
- True heading = 090 − 8 = 082°.
- Ground speed = 110 × cos(8°) − 20 × cos(50°) = 108.9 − 12.9 = 96 kt. A quartering headwind cost 14 kt.
Type those four numbers into the calculator above and you get the same 082° and 96 kt. On a manual E6B you would set 040 under the true index, mark a pencil dot 20 units up from the center, rotate to 090, and read the crab angle and ground speed under the dot. Same triangle, no trigonometry.
From indicated to true airspeed
The triangle needs true airspeed, and the airspeed indicator shows indicated. The quick rule is that TAS is about 2% higher than IAS for every 1,000 ft of altitude: at 6,000 ft, 100 kt indicated is roughly 112 kt true. For planning at typical training altitudes that rule is within a couple of knots; the POH cruise performance tables give the exact figure for your power setting and temperature. The same thin air that raises TAS also raises density altitude, which is a separate calculation with its own tool.
True to magnetic
Winds aloft (FB) forecasts are given in degrees true, so the calculator works in true and gives a true heading. To fly it, apply the magnetic variation printed on the sectional near your route: subtract east variation, add west. With a 12° east variation the 082° true heading above becomes 070° magnetic. Then correct for compass deviation from the card in the aircraft. The order for the navigation log is true course, wind correction, variation, deviation: TC → TH → MH → CH.
Time, speed & distance
Enter any two of ground speed, distance, and time and the third is computed: the classic "60-to-1" mental-math check, done exactly. Fuel burn multiplies your burn rate by time and adds an optional reserve (e.g. 0.75 hr for the 45-minute night VFR reserve).
Two mental checks worth keeping even with a calculator in hand. At 120 kt ground speed you cover 2 NM per minute, so a 46 NM leg is 23 minutes; at 90 kt it is 1.5 NM per minute. And minutes per leg equal distance × 60 ÷ ground speed, which is the same as reading the distance on the outer scale against the speed index on the wheel.
Fuel and reserves
The fuel panel multiplies burn rate by flight time and adds the reserve you enter. The legal floor for VFR under 14 CFR 91.151 is enough fuel to reach the first point of intended landing plus 30 minutes by day or 45 minutes at night, at normal cruise consumption. IFR under 91.167 is fuel to the destination, then to the alternate if one is required, then 45 minutes more. Those are minimums; most schools and clubs plan a full hour. Use the POH cruise burn for the altitude and power setting you actually intend to fly, not the placard figure, and remember that climb burns more per hour than cruise.
Unit conversions
The conversion panel covers the pairs that show up in a flight plan: nautical and statute miles (a sectional is scaled in both), knots to miles per hour and km/h, gallons to litres for fuel bought abroad or in Canada, feet to metres, Celsius to Fahrenheit for the temperature line of the METAR, and inches of mercury to hectopascals for altimeter settings outside the US. One nautical mile is 1.15 statute miles or 1.852 km; one knot is one nautical mile per hour.
Related tools
Wind is also what decides which runway you land on: the crosswind calculator splits the surface wind into headwind and crosswind components for a runway heading, and every airport page shows the favored runway from the live METAR. For descent planning, the top of descent calculator turns ground speed and altitude to lose into a distance. For the density altitude a hot day adds to your takeoff roll, see the density altitude calculator and the explainer that goes with it.
FAQ
Is this E6B accurate enough for planning?
Yes. It uses the standard trigonometric wind-triangle and density-altitude approximations taught for the FAA knowledge test. As always, it's a planning aid; verify against your POH and current data.
Can I use an online E6B on the FAA knowledge test?
No. The testing center allows a manual (slide-rule) E6B or an approved electronic flight computer with no wireless capability, and nothing that connects to the internet. Use this page to practice and to check your answers on the manual wheel; bring the wheel to the test.
What is the difference between true heading and magnetic heading?
The wind triangle works in true (referenced to true north) because winds aloft are reported in true. Convert the true heading to magnetic by applying the local variation from your chart: subtract east variation, add west ("east is least, west is best"). Then apply compass deviation from the card in the aircraft.
Why does the calculator want true airspeed instead of indicated?
Wind acts on the aircraft through the air, so the triangle needs the speed you are actually moving through the air mass. Indicated airspeed reads low at altitude because the air is thinner: roughly 2% per 1,000 ft. At 8,000 ft, 100 kt indicated is about 116 kt true.
Does it work offline?
Once the page has loaded, every calculation runs on your device with no network calls. The full SkyReady app takes this further: an offline-first logbook with currency and proficiency built in.