Practical, free calculators for structural, geotechnical, hydraulic, statistical and survey problems. Results update instantly with charts and step-by-step working.
Compute the magnetic flux density B produced by steady currents in the six most common conductor shapes, using the Biot–Savart law and Ampère's law. The calculator gives B in tesla, millitesla, microtesla and gauss, plots the field along the axis, maps the exact off-axis field of a loop, compares finite and ideal solenoids, and shows the substituted formula for every result.
Place up to eight point charges, drag them around, and watch the electric field lines and equipotential lines update live. Move the probe to read the electric field vector and potential at any point, see the net Coulomb force on every charge, or use the quick Coulomb's law calculator for two charges in any medium.
Paste a monthly rainfall series and get the SPI at 1 to 24 months using the standard McKee et al. (1993) gamma method, the drought category of every month, a list of drought events with duration and severity, and a multi-scale heatmap that shows how short dry spells grow into long droughts.
Paste annual maximum floods and get the 2- to 1000-year design floods from four distributions side by side, Gumbel confidence limits, a Gumbel probability plot with your data, a goodness-of-fit ranking, the return period of any given flood, and the full step-by-step
Estimate direct runoff depth and volume from a storm with the SCS-CN (NRCS curve number) method. Build a composite curve number from the complete TR-55 tables,
Paste a time series and get the Mann-Kendall S statistic, variance (with tie correction), Z, p-value, Kendall's τ and Sen's slope with its confidence interval. Includes the Hamed-Rao and trend-free pre-whitening corrections for autocorrelated data,
Compute asphalt tonnage, volume, quantity and total project cost for any paving job. Covers driveways, parking lots, roads and footpaths. Supports hot mix asphalt, cold mix, dense-graded, SMA and millings with accurate 2026 pricing data.
This Tool Generates a complete Gale's traverse table from bearings and distances. Calculates latitudes, departures, closing errors, Bowditch (compass rule) and Transit corrections, adjusted coordinates, adjusted bearings and lengths. Includes full step-by-step workings.
Calculate area moment of inertia (second moment of area) and mass moment of inertia for all standard shapes. Live annotated diagrams update as you type. Full step-by-step solutions, parallel axis theorem, and all unit systems.
Four equations describe every classical electric and magnetic phenomenon, from a compass needle to Wi-Fi to sunlight. This guide states each law in integral and differential form, explains what it means physically with an example,
Every power station, transformer, electric guitar pickup and wireless charger works because a changing magnetic flux induces a voltage. This guide explains magnetic flux, Faraday's law, the direction rule of Lenz's law, motional EMF, the AC generator, transformers, inductance and eddy currents, with worked examples and an animated generator you can control.
Infiltration decides how much rain becomes runoff. This guide explains the three classic infiltration models, gives the Rawls Green-Ampt parameters for all 11 soil textures, shows how to compute ponding time, and works through the φ-index and W-index.
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