Mass Calculator
Newton's Second Law (F = ma)
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Mass / Weight Converter
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How to Use This Mass Calculator
Physics homework throws two different mass problems at you on the same page—one asks for Newtons and acceleration, the other wants pounds converted to kilograms for a lab report. This tool handles both: solve for force, mass, or acceleration in SI units, or convert mass between metric and imperial units.
- Newton's Second Law — select Solve For. Choose Mass (m), Force (F), or Acceleration (a). The unknown field hides.
- Enter Force (F) and Acceleration (a). When solving for mass, type force in Newtons and acceleration in m/s², then press Calculate.
- Mass / Weight Converter — enter Value. Type the amount you want to convert.
- Pick From and To units. Select among kg, g, mg, metric tons, pounds, ounces, and stones.
- Press Convert. Read Converted Mass in the result table.
For shipping weights that include US or UK tons, use the dedicated Weight Converter. For length, temperature, volume, and other unit categories, try the Conversion Calculator. For density from mass and volume, see the Density Calculator.
Mass Calculator Formulas and Practical Applications
Newton's second law
Force, mass, and acceleration lock together like three sides of the same equation. Standard SI units are required—Newtons, kilograms, meters per second squared.
F = m × a
m = F / a
a = F / m
Example: pushing a 10 kg cart with 50 N of force produces a = 50/10 = 5 m/s² acceleration (ignoring friction).
Mass unit conversion
All mass conversions normalize through kilograms as the base unit, matching the conversion factors built into the Mass / Weight Converter section.
Standard Units Reference
- 1 kg = 2.20462 lb = 1000 g
- 1 lb = 16 oz = 453.592 g
- 1 stone = 14 lb
- 1 metric ton = 1000 kg
Frequently Asked Questions
What is the difference between mass and weight?
Mass (kg) is the amount of matter in an object and stays constant. Weight is the gravitational force on that mass (Newtons on Earth). Everyday "weighing yourself in pounds" is technically a force measurement, but colloquially people use mass and weight interchangeably.
Why do I get an error when solving for acceleration?
Mass cannot be zero when calculating acceleration (F/m), and acceleration cannot be zero when calculating mass (F/a). Enter positive non-zero values for the known variables.
How is this different from the Weight Converter?
This page adds F = ma physics alongside basic mass conversion. The Weight Converter focuses purely on unit conversion and includes US short tons and UK long tons not available in the mass converter here.
What units does the F = ma section use?
Force in Newtons (N), mass in kilograms (kg), and acceleration in m/s². Select Solve For to hide the unknown and enter the other two values.
Which mass units can I convert between?
The Mass / Weight Converter supports kg, g, mg, metric tons, pounds, ounces, and stones via the From and To dropdowns.