22 free tools, all running entirely in your browser.
Convert a speed to its Mach number — free, with a sea-level or cruise-altitude reference.
Convert between light-years, astronomical units, parsecs, and kilometers — free, using exact IAU-defined constants.
Find a height or distance from an angle of elevation using trigonometry — free, with the working shown.
Solve for a triangle’s missing sides and angles using the Law of Cosines and Law of Sines — free.
Calculate the decibel difference between two sound intensities — free, using the real logarithmic formula.
Calculate pH from hydrogen ion concentration, or the reverse — free, using the real logarithmic formula.
Solve the mirror formula for concave and convex mirrors, free — with a real ray diagram.
Solve ax² + bx + c = 0 for x, including complex roots — free and instant.
Add, subtract, multiply, or divide two fractions, automatically simplified — free and instant.
Find the greatest common divisor and least common multiple of two numbers — free and instant.
Check whether a number is prime, and see its factors if not — free and instant.
Decode a resistor’s value and tolerance from its color bands (4-band or 5-band) — free and instant.
Break a number down into its prime factors — free and instant.
Solve two linear equations in two variables — free and instant.
Find the nth term and sum of an arithmetic progression — free and instant.
Find a missing side of a right triangle, or check if three sides form one — free and instant.
Find the distance, midpoint, or a ratio-dividing point between two coordinates — free and instant.
Find the arc length, sector area, and segment area of a circle — free and instant.
Find voltage, current, resistance, or power from any two of the other three — free and instant.
Find the output voltage of a two-resistor voltage divider — free and instant.
Find the energy use and running cost of an appliance — free and instant.
Find the total resistance of resistors in series or in parallel — free, with a circuit diagram.
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