Magnetic Heading Calculator
True, magnetic or compass: put in one heading with variation and deviation and get the other two. East is least, west is best.
0 to 360°. Shown as 001–360: north is 360, not 000.
From a current chart or an official magnetic model. It changes over time.
From the compass card in the aircraft. Use 0 if you only need magnetic.
From the wind triangle. Wind from the right: correct right. With a WCA, "True" above means true course.
Copy the card next to the aircraft's compass: For is the magnetic heading, Steer is what to fly on the compass. In between, the deviation is worked out in a straight line. Saved on this device.
Training and planning aid. Take variation from a current chart or official magnetic model, deviation from the aircraft's own compass card, and fly by your approved instruments.
How your compass heading is worked out
Wind, then variation, then deviation: east is least, west is best.
- 1
Wind correction
090° + 0°
= TH 090° - 2
Variation
090° − 5°E
= MH 085° - 3
Deviation
085° + 2°W
= CH 087° - 4
Check backwards
087° − 2° + 5°
= 090° ✓
Read more: the formula, a worked example and compass card tips
A compass points to magnetic north, not true north, and every aircraft's compass has its own small error. So a course measured on a chart (true) has to be turned into what you actually steer on the compass, in three steps: wind, then variation, then deviation.
The formula
true heading = true course + wind correction angle (right +, left −)
magnetic heading = true heading − east variation, or + west variation
compass heading = magnetic heading − east deviation, or + west deviation
going back: magnetic = compass + east deviation, or − west deviation
true = magnetic + east variation, or − west variation
reciprocal = heading ± 180°
Remember it as "east is least, west is best" going from true to compass: east is taken away, west is added. Going from compass back to true, the signs flip ("east is best" coming back). Answers are kept between 001° and 360°: if a sum goes below 1, add 360; if it goes over 360, take 360 away. North is written 360, the way pilots and runways do.
Worked example
True course 090°, no wind, variation 5°E, deviation 2°W:
- True heading: 090° + 0° = 090°.
- Magnetic heading: east is least, so 090° − 5° = 085°.
- Compass heading: west is best, so 085° + 2° = 087°. Steer 087° on the compass.
- Check backwards: 087° − 2° = 085° magnetic, then 085° + 5° = 090° true. ✓
- Reciprocals: 090° + 180° = 270° true, 085° + 180° = 265° magnetic, 087° + 180° = 267° on the compass (strictly, read the deviation for the new heading from the card).
With wind: if the wind triangle gives 8° right, true heading is 090° + 8° = 098°, magnetic 098° − 5° = 093°, compass 093° + 2° = 095°. The magnetic course is 090° − 5° = 085°.
Across north: true 003° with 5°E variation is 003° − 5° = −2°, plus 360 = 358° magnetic.
Using a compass card
The card next to the compass lists headings For (magnetic) and what to Steer (compass). Deviation = For − Steer: "For 090, Steer 092" means 2°W. For a heading between two rows, take the deviation in a straight line between them. For 075° with 2°W at 060° and 2°W at 090°, it is 2°W. For 135° with 1°W at 120° and 0° at 150°, it is halfway: 0.5°W.
| For (magnetic) | Steer (compass) | Deviation |
|---|---|---|
| 360 | 001 | 1°W |
| 090 | 092 | 2°W |
| 180 | 179 | 1°E |
| 270 | 269 | 1°E |
(The sample card on this page, not a real aircraft. Use the card in your own aircraft.)
Notes
- Variation changes. Magnetic north moves, so variation drifts a little every year. Take it from a current chart, the published airport or navaid data, or an official model such as the World Magnetic Model. This page does not give values for places.
- Runways and airways are usually labelled magnetic in most of the world, but some regions (for example near the poles) publish true directions. Check which your chart uses.
- Grid and true navigation: in polar regions crews may use grid headings, which need a separate grid convergence correction not covered here.
- A magnetic compass also has turning and acceleration errors; this page covers only variation and deviation.
Formulas checked 15 October 2026. For training and planning. Fly by your approved instruments, charts and ATC.
Common questions
How do I convert true heading to magnetic heading?
Take away east variation and add west variation: "east is least, west is best". A true heading of 090° with 5°E variation is a magnetic heading of 085°. With 5°W it would be 095°.
How do I get from magnetic heading to compass heading?
Apply the deviation from the compass card in the aircraft the same way: take away east deviation, add west deviation. 085° magnetic with 2°W deviation is 087° on the compass. Deviation changes with heading, so read it for the heading you will fly.
What is the difference between variation and deviation?
Variation is the angle between true north and magnetic north where you are. It comes from the Earth and is printed on charts. Deviation is the error of one compass in one aircraft, caused by its own metal and electrics. It is written on the compass card next to the compass.
What is the order TC, WCA, TH, VAR, MH, DEV, CH?
It is the flight planning chain: true course ± wind correction angle = true heading ± variation = magnetic heading ± deviation = compass heading. Wind first, then variation, then deviation. Going from compass back to true, do the same steps in reverse with the signs flipped.
Where do I find the magnetic variation?
On a current aeronautical chart (the isogonic lines), in the airport or navaid data, or from an official magnetic model such as the World Magnetic Model. Variation slowly changes year by year, so do not rely on an old chart or a remembered figure.
Related calculators
Made by Zulu Calculator, part of AlphaZulu LLC. Formulas are shown in full and rule figures are checked against official sources; see how we build calculators.