What Is a Constant in a Science Experiment?

By Staff WriterLast Updated Mar 28, 2020 11:57:50 PM ET

Constants in an experiment refer to things that do not change when repeating trials in the experiment. The two primary types of constants are physical constants and control constants.


Most outside factors should stay the same when conducting an experiment to ensure that changes occur due to the independent variable. The opposite of constants are experimental variables, which can change as the research progresses.

Physical constants are calculated or defined quantities that cannot be altered. Examples of these constants include Avogadro’s number, pi and the speed of light. Control constants, also called control variables, refer to quantities the researcher decides to maintain while conducting an experiment. While a control constant’s value or condition may stay the same, the researcher should still record the constant to reproduce the experiment properly. Examples of control constants include temperature, pH and test duration.

Other parts of an experiment include the independent variable, which is deliberately altered, and the dependent variable, which changes according to variations made to the independent variable. Control refers to the standard that the researcher uses to compare with the results from every treatment level in the experiment. Repeated trials describe the number of times the researcher conducts the experiment to identify the effect of the independent variable on the results.