VFR and IFR cruising altitudes

East is odd, west is even, VFR adds 500. That is the whole rule in eight words, but the details around it are where the checkride questions live.

The rule

More than 3,000 feet above the surface, your magnetic course decides your cruising altitude. A magnetic course of 000 through 179 is eastbound and takes odd thousands. A magnetic course of 180 through 359 is westbound and takes even thousands. VFR adds 500 feet to whichever one applies.

So eastbound VFR is 3,500, 5,500, 7,500 and up. Westbound VFR is 4,500, 6,500, 8,500. Eastbound IFR is 3,000, 5,000, 7,000. Westbound IFR is 4,000, 6,000, 8,000.

Course, not heading

This is the detail that costs people points. The rule keys off magnetic course, the direction you are tracking over the ground, not the heading you are pointed. On a strong crosswind day those can differ by ten degrees or more, and a course of 178 with a heading of 185 is still eastbound.

The 3,000 AGL floor

Below 3,000 feet above the surface, the hemispheric rule does not apply at all. That is above the surface, not above sea level, so it moves with the terrain. In practice this is why a short local flight at 2,500 feet does not need to worry about it, and why the same 2,500 feet over higher ground might.

Above 18,000 and above 12,500

At and above 18,000 feet you are in Class A, which is IFR only, so VFR cruising altitudes stop at 17,500. Long before that, oxygen rules bite: above 12,500 cabin pressure altitude the required crew needs oxygen after 30 minutes, and above 14,000 it is continuous. For most training aircraft that makes 12,500 the practical ceiling.

When it does not apply

IFR, the altitude you fly is the one ATC assigns. The hemispheric rule governs what you file and what applies in uncontrolled airspace, but a clearance overrides it. VFR, the rule is yours to follow, and nobody is going to remind you.

Why it exists

It is a separation scheme. Two aircraft on reciprocal courses at the same cruising level would meet head on; the rule puts them 500 or 1,000 feet apart without anyone talking to anyone. The VFR 500 foot offset keeps VFR traffic clear of the IFR levels for the same reason.

The practical version

Work out the magnetic course from your departure to your destination, decide odd or even, then pick the one that gives you the best wind. EasyNavLog labels every altitude in its list as east or west from your actual course, marks the ones that fit, and ranks them by time enroute using the winds aloft forecast, so filing the wrong hemisphere takes real effort.

EasyNavLog is a planning and training aid, not a substitute for an official briefing. Verify every number against your POH or AFM, current charts and an approved weather source.