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Rock UCS and Uniaxial Compressive Strength Calculator

Uniaxial compressive strength, commonly abbreviated UCS, is the peak axial compressive stress reached by a prepared intact-rock specimen in an unconfined laboratory test. This calculator performs the transparent arithmetic for one cylindrical specimen after the user has determined that the test result is valid under the governing procedure. It does not validate the laboratory work, establish a characteristic value, or transform one specimen into the strength of an in-situ rock mass. The equation is UCS equals maximum applied axial load Pmax divided by the initial cross-sectional area A0. For a circular core with initial diameter D, A0 equals pi multiplied by D squared and divided by four. When peak load is expressed in newtons and area in square millimetres, the quotient is newtons per square millimetre, numerically equal to megapascals. GeoMiner accepts peak load in kilonewtons, newtons, or pounds-force and specimen diameter and length in millimetres, centimetres, or inches. It converts the load to newtons and the dimensions to millimetres before calculating initial area, length-to-diameter ratio, UCS in MPa, psi, and ksi, and the applicable RMR89 intact-strength band. The page begins with a worked 250 kN, 50 mm diameter, 125 mm length example. Its initial area is about 1963.495 square millimetres, its length-to-diameter ratio is 2.5, and its calculated UCS is about 127.324 MPa. The worked numbers make the equation independently repeatable; they are not a recommended test load, specimen size, acceptance criterion, or design value. Specimen length is included so the page can display the initial length-to-diameter ratio. The ratio is a record, not a standards-compliance verdict. Current governing procedures and project specifications control acceptable geometry and any correction, together with core diameter, sampling, cutting and grinding, end flatness and parallelism, moisture conditioning, dimension measurements, apparatus, load alignment and rate, failure interpretation, repetitions, statistics, and reporting. Software cannot see a damaged end, eccentric loading, machine problem, invalid failure, pre-existing discontinuity, mixed lithology, weathering transition, or transcription error. The maximum load must come from a valid uniaxial compression test rather than a point-load test, rebound estimate, field hammer result, photograph, name-based lookup, or u