A measure type for rates expressed as a percentage change per unit time (strain rates). Used extensively in geotechnical engineering for creep testing, consolidation rates, and time-dependent deformation. Units include %/s, %/min, %/h, %/d, %/month, %/year, and %/ky (per thousand years). This allows strain rates to be expressed at appropriate time scales from laboratory tests (seconds, minutes) to geological processes (years, millennia).

The unit of measure for relative rate (strain rate), expressed as percent per unit time. The time unit should be appropriate to the rate being measured.