The 1995 CIA World Factbook

by United States. Central Intelligence Agency

micro u 10-^6 10-^12 10-^18

nano n 10-^9 10-^18 10-^27

pico p 10-^12 10-^24 10-^36

femto f 10-^15 10-^30 10-^45

atto a 10-^18 10-^36 10-^54

Equivalents

Units Metric Equivalent US Equivalent

acre 0.404 685 64 hectares 43,560 feet^2

acre 4,046,856 4 meters^2 4,840 yards^2

acre 0.004 046 856 4 0.001 562 5 miles^2, kilometers^2 statute