This list contains selected positive numbers in increasing order, including counts of things, dimensionless quantities and probabilities. Each number is given a name in the short scale, which is used in English-speaking countries, as well as a name in the long scale, which is used in some of the countries that do not have English as their national language.
Smaller than (one googolth)
Mathematics – random selections: Approximately is a rough first estimate of the probability that a typing "monkey", or an English-illiterate typing robot, when placed in front of a typewriter, will type out William Shakespeare's play Hamlet as its first set of inputs, on the precondition it typed the needed number of characters. However, demanding correct punctuation, capitalization, and spacing, the probability falls to around 10−360,783. Computing: 2.2 is approximately equal to the smallest non-zero value that can be represented by an octuple-precision IEEE floating-point value. 1 is equal to the smallest non-zero value that can be represented by a quadruple-precision IEEE decimal floating-point value. 6.5 is approximately equal to the smallest non-zero value that can be represented by a quadruple-precision IEEE floating-point value. 3.6 is approximately equal to the smallest non-zero value that can be represented by an 80-bit x86 double-extended IEEE floating-point value. 1 is equal to the smallest non-zero value that can be represented by a double-precision IEEE decimal floating-point value. 4.9 is approximately equal to the smallest non-zero value that can be represented by a double-precision IEEE floating-point value. 1.5 is approximately equal to the probability that in a randomly selected group of 365 people, all of them will have different birthdays. 1 is equal to the smallest non-zero value that can be represented by a single-precision IEEE decimal floating-point value.
10−100 to 10−30
Mathematics: The chances of shuffling a standard 52-card deck in any specific order is around 1.24 (or exactly ) Computing: The number 1.4 is approximately equal to the smallest positive non-zero value that can be represented by a single-precision IEEE floating-point value.
10−30
(; 1000−10; short scale: one nonillionth; long scale: one quintillionth)
ISO: quecto- (q)
Mathematics: The probability in a game of bridge of all four players getting a complete suit each is approximately .
10−27
(; 1000−9; short scale: one octillionth; long scale: one quadrilliardth)
ISO: ronto- (r)
10−24
(; 1000−8; short scale: one septillionth; long scale: one quadrillionth)
ISO: yocto- (y)
10−21
(; 1000−7; short scale: one sextillionth; long scale: one trilliardth)
ISO: zepto- (z) Mathematics: The probability of matching 20 numbers for 20 in a game of keno is approximately 2.83 × 10−19. Mathematics: The odds of a perfect bracket in the NCAA Division I men's basketball tournament are 1 in 263, approximately 1.08 × 10−19, if coin flips are used to predict the winners of the 63 matches.
10−18
(; 1000−6; short scale: one quintillionth; long scale: one trillionth)
ISO: atto- (a) Mathematics: The probability of rolling snake eyes 10 times in a row on a pair of fair dice is about .
10−15
(; 1000−5; short scale: one quadrillionth; long scale: one billiardth)
ISO: femto- (f) Mathematics: The Ramanujan constant, is an almost integer, differing from the nearest integer by approximately .
10−12
(; 1000−4; short scale: one trillionth; long scale: one billionth)
ISO: pico- (p) Mathematics: The probability in a game of bridge of one player getting a complete suit is approximately (). Biology: Human visual sensitivity to 1000 nm light is approximately of its peak sensitivity at 555 nm.
10−9
(; 1000−3; short scale: one billionth; long scale: one milliardth)
ISO: nano- (n) Mathematics – Lottery: The odds of winning the Grand Prize (matching all 6 numbers) in the US Powerball lottery, with a single ticket, under the rules , are 292,201,338 to 1 against, for a probability of (). Mathematics – Lottery: The odds of winning the Grand Prize (matching all 6 numbers) in the Australian Powerball lottery, with a single ticket, under the rules , are 134,490,400 to 1 against, for a probability of (). Mathematics – Lottery: The odds of winning the Jackpot (matching the 6 main numbers) in the UK National Lottery, with a single ticket, under the rules , are 13,983,815 to 1 against, for a probability of ().
10−6
(; 1000−2; long and short scales: one millionth)
ISO: micro- (μ)
