Growth rate is measured by increased growth per unit time. Growth in an organism or its part can occur in many different ways.

When the total growth of the living system is measured and compared in a particular unit time is referred as absolute growth rate. This growth rate is for that particular living system in that time interval and not compared with other living system.

Absolute growth = Growth in given time period = Growth (final time) - Growth (initial time)

Absolute growth of A = Growth A'-Growth $\mathrm{A}=10-5=5\mathrm{ }{\mathrm{c}\mathrm{m}}^2.$

Absolute growth of B = Growth B'-Growth $\mathrm{B}=55-50=5\mathrm{ }{\mathrm{c}\mathrm{m}}^2$ .

When the growth of living system measured per unit time is expressed on a common basis is referred to as relative growth rate. It is more of a comparative growth rate between initial time period and current time period.

Relative growth rate = Growth in given time/Initial growth*100

Relative growth rate A = (Final Growth - Initial Growth)/Initial Growth*

= (10-5)/5*100 = 100%

Relative growth rate B= (Final Growth - Initial Growth)/Initial Growth*

= (55-50)*100/50 = 10%