Ohm’s law
Find current and power from voltage and resistance.
67 calculators
Find current and power from voltage and resistance.
Solve for density, mass, or volume with common metric units.
Calculate the energy of a moving object.
Estimate DC voltage drop from current, one-way length and conductor resistance.
Calculate equivalent resistance for two resistors in series and parallel.
Calculate mass from force and acceleration.
Calculate solution molarity from amount of substance and solution volume.
Calculate molar mass from counts of two elements and their atomic masses.
Estimate wind-chill temperature using the Canadian/US Celsius-km/h equation.
Estimate heat index in Fahrenheit from temperature and relative humidity.
Estimate dew point from Celsius temperature and relative humidity.
Calculate DC or resistive-circuit power, current, energy, and cost.
Estimate balanced three-phase real power.
Find equivalent capacitance for two capacitors.
Estimate device runtime from battery energy and load.
Calculate wavelength from frequency and propagation speed.
Estimate real, apparent, and reactive power for a single-phase AC load.
Calculate an ideal transformer voltage, current, and turns relationship.
Compare annual energy and cost before and after a lighting upgrade.
Calculate ideal buoyant force from displaced-fluid volume and density.
Resolve launch velocity into horizontal and vertical components to estimate projectile range, flight time and height at equal launch and landing elevations.
Estimate how long an object dropped from rest takes to fall through a known height and the speed it reaches just before impact.
Find the minimum escape speed at a specified distance from a central mass, using gravitational potential energy and a zero speed at infinity.
Calculate the time for a circular orbit and its constant orbital speed from the central mass and the centre-to-centre orbital radius.
Calculate the inward acceleration and force required to keep a mass moving at a given speed around a circular path of known radius.
Calculate torque magnitude using force, the distance from the pivot and the angle between them; a parallel force produces no torque.
Multiply moment of inertia about a fixed axis by angular velocity to find signed angular momentum; reversing rotation reverses its sign.
Calculate rotational kinetic energy from moment of inertia and the square of angular velocity; rotation direction does not change the energy.
Calculate energy stored in a stretched or compressed spring and the signed restoring force, which acts opposite the entered displacement.
Find the oscillation period and frequency of a mass attached to an ideal spring; a heavier mass slows the oscillation while stiffness speeds it up.
Estimate the period and frequency of a small-angle pendulum using its pivot-to-bob length and local gravity, without needing the bob mass.
Calculate the pressure increase below the surface of a stationary liquid from density and depth; atmospheric pressure is excluded from this gauge value.
Apply equal fluid pressure to two pistons to find output force and mechanical advantage; the piston areas must use the same square-centimetre unit.
Multiply the internal cross-sectional area of a circular pipe by mean fluid speed to find volume flow per second and per minute.
Compare inertial effects with viscous effects using density, mean speed, characteristic length and dynamic viscosity to obtain a dimensionless Reynolds number.
Convert vacuum wavelength in nanometres into the energy of one photon in joules and electronvolts using Planck’s constant and light speed.
Estimate net radiated power exchanged with large surroundings from emissivity, surface area and the difference of fourth powers of absolute temperatures.
Find the wavelength of maximum blackbody spectral radiance per unit wavelength from absolute temperature; the frequency-spectrum peak is different.
Estimate intensity at a new distance from an isotropic point source by multiplying the original intensity by the squared distance ratio.
Use the thin-lens equation to find signed image distance and magnification; a negative image distance represents a virtual image.
Calculate gas pressure from amount in moles, absolute temperature and volume using the ideal gas relationship; volume is entered in cubic metres.
Estimate heat added or removed when a material changes temperature using its mass and specific heat, keeping the sign of the temperature change.
Calculate a solid’s change in length and final length from its linear expansion coefficient, original length and signed temperature change.
Convert solute mass to moles using molar mass, then divide by kilograms of solvent to obtain molality independently of solution volume.
Divide each component’s amount in moles by the total amount to obtain two complementary mole fractions that sum to one.
Calculate mechanical work from force, displacement and their included angle.
Find impulse and momentum change from average force over a time interval.
Find the restoring force of a spring from stiffness and signed displacement.
Convert an acoustic intensity and reference intensity into a decibel level.
Convert a decibel difference into power and equal-impedance amplitude ratios.
Estimate frequency heard by a stationary observer when a sound source moves toward or away from them.
Find the beat rate produced by two nearby frequencies.
Compare object speed to the local speed of sound.
Estimate the Newtonian attraction between two point or spherical masses.
Find gravitational acceleration outside an ideal spherical body.
Find average angular acceleration from initial and final angular velocities.
Calculate angular displacement under constant angular acceleration.
Combine translational and rotational energy for an object rolling without slip.
Estimate steady heat conduction through one flat homogeneous layer.
Find the ideal maximum heat-engine efficiency between two absolute temperatures.
Calculate thermal efficiency and rejected heat from heat input and work output.
Calculate the energy magnitude for a phase change at constant temperature.
Estimate electrostatic force between two point charges in vacuum.
Calculate the radial electric field of a point charge in vacuum.
Find the electric potential of a point charge relative to infinity.
Find the critical viscous damping coefficient for a single mass-spring oscillator.
Infer an average convective heat-transfer coefficient from heat flow, area and temperature difference.
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