       Concrete Strengths Rebar Average Rebar Weights Welded Wire Mesh Pan Slabs Slab Flatness and F-numbers         Concrete Strengths Nominal MPa values of equivalent psi concrete strengths In metric, concrete strength is denominated in megapascals (MPa) In imperial, concrete strength is denominated in pounds per square inch (psi) 2500 psi = 18 MPa (17.23 MPa exact) 3000 psi = 20 MPa (20.67 MPa exact) 3500 psi = 25 MPa (24.12 MPa exact) 4000 psi = 30 MPa (27.57 MPa exact) 5000 psi = 35 MPa (34.46 MPa exact) 6000 psi = 40 MPa (41.35 MPa exact) Use 0.0068915 to convert psi to MPa Newtons, psi, concrete strength and prestressed slabs Concrete strengths are customarily denominated in psi (pounds per square inch) in the imperial system and in MPa's (megapascals) in metric. These are units of pressure. The newton (N) is a measure of force. 1 newton is that force which pushes 1 gram of matter with an acceleration of 1 centimeter per second per second (or per second ²) or, equivalently, the force that accelerates 1 kilogram of matter to 1 meter per second ². Force = mass x acceleration Velocity is a measure of constant speed (i.e., meters per second, miles per hour, furlongs per fortnight) Velocity is speed in a certain direction Acceleration is the rate of change in velocity over time Acceleration can be either positive or negative (deceleration) 1 N = 1 kg x (1 meter / second ²) -----> 1 N = 1 kg.meter / second ² 1 N = 1 g x (1 cm / second ²) When you apply the force of 1 newton to a 1 meter ² area, you have pressure. Pressure = force per area Pressure can be measured in pascals (Pa). 1 Pa = 1 N / meter ² The strength of concrete is commonly stated, in metric, in megapascals (MPa). 1 MPa = 1,000,000 Pa = 1,000,000 Newtons / meter ²