A ratio is the relationship in quantity or degree between two things: “The ratio of men to women on the construction site was ten to one.” This means there were ten men present and one woman.

Use the word ratio when you want to make a comparison between two things. A ratio basically expresses a proportion. Often used in mathematics, the word ratio has many real world uses as well. This word is useful for everything from making salad dressing (an oil-to-vinegar ratio of three to one) to selecting a school for a child (consider the student-to-teacher ratio when making your decision).

Definitions of ratio
  1. noun
    the relation between things (or parts of things) with respect to their comparative quantity, magnitude, or degree
    synonyms: proportion
    see moresee less
    type of:
    magnitude relation, quantitative relation
    a relation between magnitudes
  2. noun
    the relative magnitudes of two quantities (usually expressed as a quotient)
    see moresee less
    show 48 types...
    hide 48 types...
    gross margin, margin of profit, profit margin
    the ratio gross profits divided by net sales
    (chemistry) the ratio of the total mass of an element in the earth's crust to the total mass of the earth's crust; expressed as a percentage or in parts per million
    (physics) the ratio of the number of atoms of a specific isotope of an element to the total number of isotopes present
    albedo, reflective power
    the ratio of reflected to incident light
    aspect ratio
    the ratio of the width to the height of a tv picture
    (sports) the ratio of successful performances to opportunities
    breadth index, cephalic index, cranial index
    ratio (in percent) of the maximum breadth to the maximum length of a skull
    the ratio of the output to the input of any system
    facial index
    the ratio (in percent) of the maximum width to the maximum height of the face
    f number, focal ratio, speed, stop number
    the ratio of the focal length to the diameter of a (camera) lens system
    frequency, relative frequency
    the ratio of the number of observations in a statistical category to the total number of observations
    haematocrit, hematocrit, packed cell volume
    the ratio of the volume occupied by packed red blood cells to the volume of the whole blood as measured by a hematocrit
    I.Q., IQ, intelligence quotient
    a measure of a person's intelligence as indicated by an intelligence test; the ratio of a person's mental age to their chronological age (multiplied by 100)
    load factor
    (aeronautics) the ratio of an external load to the weight of the aircraft (measured in g)
    loss ratio
    the ratio of the annual claims paid by an insurance company to the premiums received
    Mach number
    the ratio of the speed of a moving body to the speed of sound
    the ratio of the size of an image to the size of the object
    mechanical advantage
    the ratio of the force exerted by a machine to the force applied to it
    fuel consumption rate, gas mileage, gasoline mileage, mileage
    the ratio of the number of miles traveled to the number of gallons of gasoline burned
    betting odds, odds
    the ratio by which one better's wager is greater than that of another
    magnitude, order of magnitude
    a number assigned to the ratio of two quantities; two quantities are of the same order of magnitude if one is less than 10 times as large as the other; the number of magnitudes that the quantities differ is specified to within a power of 10
    output-to-input ratio
    the output power of a transducer divided by the input power
    (epidemiology) the ratio (for a given time period) of the number of occurrences of a disease or event to the number of units at risk in the population
    P/E ratio, price-to-earnings ratio
    (stock market) the price of a stock divided by its earnings
    (economics) the ratio of the quantity and quality of units produced to the labor per unit of time
    a ratio of two quantities that is constant
    the ratio of two quantities to be divided
    index of refraction, refractive index
    the ratio of the velocity of light in a vacuum to that in a medium
    relative humidity
    the ratio of the amount of water in the air at a give temperature to the maximum amount it could hold at that temperature; expressed as a percentage
    respiratory quotient
    the ratio of the volume of carbon dioxide expired to the volume of oxygen consumed by an organism or cell in a given period of time
    factor of safety, safety factor
    the ratio of the breaking stress of a structure to the estimated maximum stress in ordinary use
    S/N, signal-to-noise, signal-to-noise ratio, signal/noise, signal/noise ratio
    the ratio of signal intensity to noise intensity
    (chemistry) the relation between the quantities of substances that take part in a reaction or form a compound (typically a ratio of whole integers)
    time constant
    the ratio of the inductance of a circuit in henries to its resistance in ohms
    employee turnover, turnover, turnover rate
    the ratio of the number of workers that had to be replaced in a given time period to the average number of workers
    the ratio of the gross weight of an airplane to some factor determining its lift
    (geometry) a ratio describing the shape of a conic section; the ratio of the distance between the foci to the length of the major axis
    the quotient obtained when the magnitude of a part is divided by the magnitude of the whole
    commensurateness, correspondence, proportionateness
    the relation of corresponding in degree or size or amount
    batting average, hitting average
    (baseball) a measure of a batter's performance; the number of base hits divided by the number of official times at bat
    fielding average
    (baseball) a measure of a fielder's performance; the number of assists and putouts divided by the number of chances
    figure of merit
    a numerical expression representing the efficiency of a given system, material, or procedure
    adult intelligence
    the average IQ of the adults in a given population
    borderline intelligence
    the minimal IQ required for someone to function normally and independently in the world (without some form of institutional assistance)
    power loading
    the ratio of the weight of an airplane to its engine power
    span loading
    the ratio of the weight of an airplane to its wingspan
    wing loading
    the ratio of the weight of an airplane to its wing area
    incidence, relative incidence
    the relative frequency of occurrence of something
    type of:
    magnitude relation, quantitative relation
    a relation between magnitudes
Word Family

Test prep from the experts

Boost your test score with programs developed by Vocabulary.com’s experts.

  • Proven methods: Learn faster, remember longer with our scientific approach.
  • Personalized plan: We customize your experience to maximize your learning.
  • Strategic studying: Focus on the words that are most crucial for success.


  • Number of words: 500+
  • Duration: 8 weeks or less
  • Time: 1 hour / week


  • Number of words: 500+
  • Duration: 10 weeks or less
  • Time: 1 hour / week


  • Number of words: 700+
  • Duration: 10 weeks
  • Time: 1 hour / week