Gratis online tools

Calculate Richter magnitude from seismograph amplitude and distance, explore effects and energy for any ML value, or compare two magnitudes. Free, browser-based.

Calculate wind chill (feels-like temperature) from air temperature and wind speed. Uses the official NWS / Environment Canada 2001 formula with frostbite risk guidance. Free, browser-based.

Calculate air density from temperature, pressure, and humidity, or from altitude. Shows kg/m³, virtual temperature, speed of sound, and comparison to sea-level standard. Free, browser-based.

Convert between altitude and atmospheric pressure using the barometric formula or ISA standard atmosphere. Pressure in hPa, inHg, kPa, and more. Free, browser-based.

Calculate soil bulk density, moisture content, porosity, and void ratio from sample mass and volume. Supports metric (g, cm³) and imperial (lb, ft³). Free, browser-based.

Calculate rock bulk density from mass and volume, rectangular blocks, or drill cores. Porosity from grain density. Compare to typical granite, basalt, limestone, and more. Free, browser-based.

Calculate rainfall volume from catchment area and depth, estimate storm runoff with a runoff coefficient, or compute rainfall intensity (mm/hr). Metric and imperial units. Free, instant, browser-based.

Calculate volumetric flow rate Q = A × v for pipes and open channels, estimate flow with Manning's equation, or convert between L/s, GPM, CFS, and m³/s. Metric and imperial units. Free, instant, browser-based.

Calculate river discharge Q from channel width, depth, and mean velocity (velocity–area method), trapezoidal cross-sections with bank slope, or Manning's equation. Results in m³/s, L/s, and CFS with river size classification. Free, browser-based.

Calculate ultimate and allowable soil bearing capacity using Terzaghi's equation for strip, square, and circular footings. Enter cohesion, friction angle φ, unit weight, depth, and footing width. Compare applied pressure to q_allow. Metric and imperial units. Free, browser-based.

Calculate cement, sand, aggregate, and water quantities for concrete mixes. Design by volume, cement bags, or grade presets (M10–M25). Enter mix ratio 1:S:A and water–cement ratio. Metric (m³, kg) and imperial (yd³, lb) units. Free, browser-based.

Calculate steel weight for round bar, rebar, square bar, flat bar, plate, and pipe. Enter dimensions and quantity — get total kg or lb, weight per meter, and volume. Carbon steel density 7850 kg/m³. Metric and imperial units. Free, browser-based.