Vector Addition Calculator Up to 10 vectors can be
input.
Vector Addition Tutorial

Parallel Resistor Calculator Up to 10 values can be input.
Resistor Color Code Calculator A handy tool even though it is not essential for studying physics.
American Wire Gauges NOT a calculator but a handy reference that states diameters of wire sizes from number "0000" to number "40" (in inches and millimeters) as well as resistance in ohms per 1,000 feet and ohms per kilometer.

Electromagnetic Frequency and Wavelength Calculator Also calculates photon energy.
Sound Frequency and Wavelength Calculator

Ohm's Law Ultra Calculator

Resonant Frequency Calculator

Gravitational Force Calculator

Relativity Calculator Calculates
Relativistic Changes In Time Length and Mass For Objects Approaching Light Velocity.

Mass To Energy Calculator Uses the Legendary
Formula E=mc² to compute the energy equivalent of a mass.
Energy To Mass Calculator Same as above but this calculates the mass equivalent of a specified amount of energy.

Pendulum Period Calculator Calculates
Large Amplitude Pendulum Periods up to θ^{14} and calculates exact pendulum periods using the (agm) arithmeticgeometric mean.

Atmospheric Pressure Calculator Calculates Altitude when you input Atmospheric Pressure and
Calculates Atmospheric Pressure when you input Altitude.

The Six Simple Machines
These aren't calculators but are nonetheless informative.
The Index Page
The Lever
The Pulley
The Wheel and Axle
The Inclined Plane
The Wedge
The Screw
∎ ∎ ∎ ∎ ∎ ∎ ∎
Classical Mechanics Not a calculator. Instead it describes the units used in classical mecahanics and defines the quantites used, such as velocity, acceleration, force, energy and power.
