And if the balls had to sit in neat rows?

Roughly 17 million, at about 340 a cubic foot instead of 400.

What changes if the interviewer means a freighter version with no seats?

The seats come out. That leaves about 54,000 cubic feet after the floor and cockpit, or roughly 22 million balls.

How confident are you in 400 balls per cubic foot?

Fairly. A neat grid gives 343 and loose balls settle a little tighter, so 350 to 450 covers it, and the cabin's volume is the shakier input.

How many golf balls fit in a Boeing 747?

About 20 million. Model the body as a tube 20 feet across and 200 feet long, about 60,000 cubic feet, then subtract seats and galleys to leave 50,000. Loose golf balls fit about 400 per cubic foot, giving 20 million.

Updated October 20, 2026

How a 90-point answer starts

I'll assume the seats stay in and we fill the cabin and cargo hold, not the wings. My approach is the volume of the plane's body divided by the space one golf ball takes up.

See the full answer, the 50 and 70 versions, and what moves each score up.

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The numbers, step by step

The plane's body is treated as a tube 200 feet long and 20 feet across, with pi taken as 3 and seats left in.

Volume of the body3 × 10 ft × 10 ft × 200 ft: 60,000 cubic feet
Space left with seats and equipment in60,000 − (400 seats × 10 + 6,000): 50,000 cubic feet
Volume of one ballhalf of a 5 cubic inch cube: 2.5 cubic inches
Space one ball takes up2.5 ÷ 0.625, a bit under two thirds full: 4 cubic inches
Balls per cubic foot1,700 cubic inches ÷ 4: 425
Golf balls with seats in50,000 × 400 (425 rounded down): 20 million
Check: neat grid in a cubic foot7 × 7 × 7: 343 balls
Golf balls with seats out(60,000 − 6,000) × 400 = 54,000 × 400: 21.6 million
Golf balls in the bare tube60,000 × 400: 24 million

What the interviewer listens for

Do you say what you're filling, such as cabin, cargo hold, seats in or out?
Do you reason the plane's dimensions out loud and not quote them as facts?
Do you allow for the gaps between round balls?
Do you keep feet and inches straight when you convert?
Do you end with a range and say what drives it?

Common mistakes

Dividing the plane's volume by the ball's own volume, as if balls stacked with no air between them.Loose spheres leave about a third of the space empty.
Cubic feet divided by cubic inches, without converting, leaves the answer about 1,700 times too small.
A round tube holds about three quarters of the square box around it, so a box 20 feet by 20 feet overstates the space.
Quoting the plane's length from memory.The interviewer wants to see the size built from seats and rows, so a recalled figure earns nothing even when it's right.

Likely follow-ups

And if the balls had to sit in neat rows?Roughly 17 million, at about 340 a cubic foot instead of 400.
What changes if the interviewer means a freighter version with no seats?The seats come out. That leaves about 54,000 cubic feet after the floor and cockpit, or roughly 22 million balls.
How confident are you in 400 balls per cubic foot?Fairly. A neat grid gives 343 and loose balls settle a little tighter, so 350 to 450 covers it, and the cabin's volume is the shakier input.

“Market sizing used to take me forever because I'd overthink every assumption. The drills helped me pick reasonable numbers and get to an estimate faster.”

Theo M.McKinsey business analyst offer

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