The Standard Unit of Area Measurement of the United States: The Football Field

1 football field   =   5351 square meters
1 square meter     =   1.869e-4 football fields

Of course the regulation Canadian football field is 150 yards (110 yards in the field of play plus a 20 yard end zone at each end) by 65 yards wide. Thus, 137.16 metres x 59.43 metres.

So in Canada:
1 football field = 8152 square metres
1 square metre = 1.227 *10^(-4) football fields
1 football field = 9750 square feet
1 square foot = 1.026 *10^(-4) football fields

So for maximum precision one should say "An ounce of aerogel has the surface area of 10 NFL football fields (slightly less in Canada)".

How do Americans play football on such a tiny field? Well, with 1 less player per side, I know, but still ...