Science & Engineering Calculators
Solve physics, chemistry and electronics with Ohm's law, half-life and molarity.
Updated June 2026 · Free · No sign-up
This cluster brings together the standard formula-based calculators used across physics, chemistry and electrical engineering, useful for lab work, coursework and practical projects. Physics and chemistry are covered by the Half-Life, Speed/Distance/Time, Density, Molarity and Molecular Weight calculators, each applying the textbook relationship for the quantity you want.
On the electronics side, the Ohm's Law calculator links voltage, current, resistance and power, the Resistor Color Code calculator decodes colour bands into a resistance and tolerance, and the Voltage Drop calculator estimates losses along a cable run. Every tool states the formula it uses so the result can be checked or reproduced by hand.
All Science & Engineering Calculators
Half-Life Calculator
Calculate radioactive decay, remaining quantity, and elapsed time using half-life formula.
Speed / Distance / Time Calculator
Calculate speed, distance, or time from any two known values.
Density Calculator
Calculate density, mass, or volume from any two known values using density = mass / volume.
Ohm's Law Calculator
Calculate voltage, current, resistance, or power using Ohm's Law (V = IR).
Resistor Color Code Calculator
Decode resistor color bands to find resistance value, tolerance, and power rating.
Voltage Drop Calculator
Calculate voltage drop in electrical wiring based on wire gauge, length, and current draw.
Molarity Calculator
Calculate molarity, moles of solute, or volume of solution for any chemical.
Molecular Weight Calculator
Calculate molar mass of chemical compounds from a chemical formula (e.g., H₂O, NaCl).
Frequently asked questions
What is Ohm's law and how does it relate to power?
Ohm's law states V = I times R, where V is voltage in volts, I is current in amperes and R is resistance in ohms. Electrical power is P = V times I, which can be combined with Ohm's law to give P = I squared times R or P = V squared / R. The Ohm's Law calculator finds any of these four quantities from the other known values.
How is half-life used to calculate radioactive decay?
The remaining quantity after time t is N = N0 times (1/2) to the power (t / T), where N0 is the starting amount and T is the half-life. After one half-life, half the sample remains; after two half-lives, a quarter remains, and so on. Rearranging the formula also lets you solve for the elapsed time or the original amount.
What is molarity and how do you calculate it?
Molarity is the concentration of a solution in moles of solute per litre of solution, with units of mol/L (M). It is calculated as molarity = moles of solute / volume of solution in litres. Moles of solute can be found from mass divided by molar mass, which is why the Molarity and Molecular Weight calculators are often used together.
How do you find the density of a substance?
Density is mass divided by volume, written rho = m / V, and is commonly expressed in kg per cubic metre or g per cubic cm. Rearranging gives mass = density times volume and volume = mass / density, so any one of the three can be found from the other two. For reference, pure water has a density of about 1 g per cubic cm at 4 degrees Celsius.
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