The Maximum Elevation Figure, the Big Blue Numbers in Every Sectional Quadrangle, and How to Pick a Cruise Altitude That Actually Clears the Highest Thing Out There

The Maximum Elevation Figure (MEF) is the blue two-part number printed inside each grid square, or quadrangle, of a sectional chart. It tells you the height above sea level of the tallest known obstacle - terrain or man-made structure - in that box, with a safety buffer already added. Fly above the highest MEF along your route, add clearance for weather and terrain effects, and you have a cruise altitude that clears everything the chart makers knew about.

What Is the Maximum Elevation Figure on a Sectional Chart?

The FAA divides every sectional into a grid bounded by lines of latitude and longitude. Inside each grid square, chart makers identify the single highest object - a mountain peak, a radio tower in a field, or a ridge line - and record its elevation.

They then add a buffer for the height of a man-made structure, round the figure up, and add a little extra cushion. That final rounded number, printed in blue, is the Maximum Elevation Figure.

Think of the MEF as a promise: nothing in that box sticks up higher than this number. Fly above it and you will not hit anything the chart depicts. Fly below it and all bets are off, because a 200-foot tower may be reaching right up toward you.

How Do I Read the Big Blue Numbers?

The MEF uses two sizes of type. The large number represents thousands of feet, and the small raised number represents hundreds of feet.

So a box showing a large 1 and a smaller 27 is not 1,027 feet. It reads 12,700 feet above sea level - the top of everything in that square.

How Do I Use the MEF to Pick a Cruise Altitude?

Start by drawing your course line straight from departure to destination. Suppose you’re flying a 130-nautical-mile cross-country.

Now run your finger along that entire line and check the MEF in every grid box the course passes through - not just your departure and arrival boxes. Your airplane flies over all of them.

Find the highest MEF along the whole route. Say most boxes read around 3,000 to 4,000 feet, but one box in the middle, where your line clips higher terrain, reads 7,500 feet. That 7,500 is now your floor - the tallest thing you’ll cross.

How Much Clearance Should I Add Above the MEF?

Clearing an obstacle by one foot is never the goal. A common instructor rule of thumb is to add at least 1,000 feet above the highest MEF over flat country, and 2,000 feet over rising terrain or mountains.

The extra margin matters because the MEF clears the obstacle, not the air around it. Wind flowing over a ridge creates downdrafts, mechanical turbulence, and - on a bad day - mountain wave that can push you down faster than a trainer can climb.

In our example, the highest MEF is 7,500 feet. Add 1,000 feet and you have a planning floor of 8,500 feet.

What Does the VFR Cruising Altitude Rule Require?

FAR 91.159, the VFR cruising altitude rule, applies when you’re more than 3,000 feet above the ground:

• On a magnetic course of 0° through 179° (generally eastbound), fly odd thousands plus 500: 5,500, 7,500, 9,500.
• On a magnetic course of 180° through 359° (generally westbound), fly even thousands plus 500: 6,500, 8,500, 10,500.

For our eastbound leg needing at least 8,500 feet, the next legal odd-plus-500 altitude is 9,500 feet. That fits the rule and sits a full 2,000 feet above the 7,500-foot MEF - an altitude you can defend to any examiner and to yourself when the air gets rough at night.

What Will a Checkride Examiner Look For?

The Airman Certification Standards (ACS) lists cross-country planning as a task, and the examiner wants to see a specific chain of reasoning. They’re checking that you selected a cruise altitude with terrain and obstruction clearance in mind, that it complies with the cruising altitude rule for your direction, and that you can explain why.

If asked “Why 9,500?”, the wrong answer is a shrug. The right answer: the highest MEF on my route is 7,500, I want at least 1,000 feet of clearance, and 9,500 is the correct VFR altitude for an eastbound course. That hands the examiner the whole reasoning chain - the mark of a pilot who thinks.

Should I Fly Over the High Terrain or Route Around It?

Real flying complicates the straight line. What if 9,500 feet drops you into a headwind that eats your groundspeed, or a cloud layer at 8,000 feet leaves you scud running against the bases?

Look again at where the high ground actually is. If the only reason your floor is so high is one grid box where the line clips a corner of terrain, shifting your course a few miles could route around that box entirely. Now your highest MEF might be 5,000 feet, and 6,500 feet becomes a comfortable westbound altitude with better wind.

That’s the deeper value of the MEF: it shows you where the high ground is, so you can decide whether to climb over it or go around. A slightly longer route at a lower, smoother, faster altitude can beat a straight line that drags you up into the wind and weather.

Can My Airplane Actually Climb Above the MEF?

Reading the MEF is only step one. Confirming your airplane can reach that altitude - on this day, at this weight, at this temperature - is step two, and it’s the one pilots skip.

Consider a straight-line cross-country over mountains where the highest MEF is 11,000 feet. The pilot knows the rule and plans for 12,500 feet. On paper, perfect.

Then comes a warm day. Density altitude is high. The fully loaded trainer, with two people and full fuel, is climbing maybe 200 feet per minute in the thin air. It never reaches 12,500 before the ridge. The pilot ends up staring at rising ground with an airplane that won’t climb, boxed into a canyon looking for room to turn around.

The chart never lied. What killed the plan was assuming the airplane could reach the altitude the chart demanded. Pull the performance charts, run the density altitude, and know your real climb rate for the conditions you’ll fly - not the book figure for a new airplane on a cold day at sea level.

Key Takeaways

• The Maximum Elevation Figure (MEF) is the blue number in each sectional grid square showing the height of the tallest obstacle there, plus a buffer.
• Read it in two parts: the large number is thousands of feet, the small raised number is hundreds. A large 1 and small 27 means 12,700 feet.
• Trace your entire course box by box, circle the highest MEF, and treat it as your floor - then add 1,000 feet over flat land or 2,000 feet over mountains.
• Combine that floor with FAR 91.159 (odd+500 eastbound, even+500 westbound) to choose a legal, safe cruise altitude.
• The MEF tells you how high the terrain is; your performance and density-altitude planning tells you whether you can actually climb over it. You need both.