Calculator
Example data table
| Weight | Gravity (m/s²) | Mass (kg) | Notes |
|---|---|---|---|
| 98.0665 N | 9.80665 | 10.0000 | Standard Earth gravity example |
| 32.1740 lbf | 9.80665 | 14.5939 | 1 slug mass under standard gravity |
| 1000 N | 1.62 | 617.2840 | Same force produces larger mass on the Moon |
| 75 kgf | 9.80665 | 75.0000 | kgf uses standard gravity by definition |
| 200 lbf | 3.711 | 241.0400 | Illustrative Mars gravity conversion |
Values are rounded for readability. Your selected rounding may differ.
Formula used
Weight is the gravitational force on a mass. The relationship is:
- W = m × g
- m = W / g (used by this calculator)
Where W is weight (force) in Newtons, m is mass in kilograms, and g is gravitational acceleration in m/s².
How to use this calculator
- Enter your weight value and select its unit.
- Select a gravity preset, or choose Custom and type g.
- Pick rounding and optional scientific notation if needed.
- Click Calculate to view mass and unit conversions.
- Use CSV or PDF buttons to save your results.
For best accuracy, use force units (N, lbf) with a realistic gravity value.
Notes and limitations
- This is a physics conversion tool, not a medical estimator.
- Local gravity varies slightly with altitude and latitude.
- “kgf” and “gf” are defined using standard gravity, g₀.
Article
1) Weight and mass are not the same
Weight is a force measured in Newtons or pound-force. Mass is an amount of matter measured in kilograms, pounds-mass, or slugs. This calculator uses the physics relationship W = m × g to convert a force into a mass using a chosen gravitational acceleration.
2) Gravity is the conversion key
The same weight value can imply very different mass if gravity changes. For example, using a Moon gravity near 1.62 m/s² instead of Earth’s standard 9.80665 m/s² increases the computed mass for the same force by about 6.05×.
3) Typical gravity values you may use
Common presets include Earth standard (9.80665 m/s²), Earth equator (9.7803 m/s²), Earth pole (9.8322 m/s²), Mars (3.711 m/s²), and Jupiter (24.79 m/s²). Choose Custom when your project specifies local or simulated g.
4) Why unit conversion happens first
Internally, every input is converted to Newtons so one consistent formula is applied. Examples: 1 lbf = 4.448221615 N, 1 kgf = 9.80665 N, and 1 dyne = 1×10⁻⁵ N. This keeps results consistent across engineering and lab inputs.
5) Understanding the output units
The primary result is kilograms. The tool also provides grams, tonnes, pounds-mass, stones, and slugs. A useful reference is 1 slug = 14.5939 kg. Seeing multiple units helps you match worksheets, mechanical drawings, or textbook examples.
6) Rounding and scientific notation
For quick checks, 2–4 decimals are often enough. For calibration work or small forces, scientific notation prevents losing detail. Increasing decimals will not change physics, but it can reduce rounding error when you copy values into a spreadsheet or report.
7) Quick sanity checks with real numbers
Under standard Earth gravity, 98.0665 N corresponds to 10 kg. Also, a 32.174 lbf force under standard gravity corresponds to about 1 slug of mass. Use these checks to confirm unit choices before exporting.
8) Exporting results for documentation
After calculating, download the result table as CSV for data logging, or save a clean PDF for attachments. Exports include your input weight, converted Newtons, gravity value, and mass in each unit so your results are reproducible and easy to audit.
FAQs
1) What gravity should I choose for everyday work?
Use Earth (standard) for general conversions. Choose equator or pole when you need slightly different g values. Use Custom when a lab, simulation, or specification provides an exact acceleration.
2) Why does the same weight give different mass on different planets?
Because the calculator treats weight as a force. Mass is computed by dividing that force by g. Smaller g means a larger mass value is needed to produce the same force.
3) Is kilogram-force the same as kilogram?
No. Kilogram-force is a force unit. It equals the force produced by 1 kg under standard gravity. Kilogram is a mass unit, independent of gravity.
4) When should I use slugs?
Slugs are common in US engineering mechanics. If your formulas use lbf and feet-based systems, slugs keep equations consistent without mixing force and mass units.
5) Can I enter very small forces like dynes?
Yes. Use the dyne unit for small forces. For tiny values, enable scientific notation and increase decimals so the displayed result keeps sufficient precision for your analysis.
6) What if I only know mass and want weight?
This page converts weight to mass. If you know mass, compute weight using W = m × g. Use the same gravity value you would choose here to stay consistent.
7) Do exports include my chosen options?
Yes. Exports include your entered weight, the converted Newton value, the gravity used, and the mass outputs. This makes it easier to reproduce calculations and verify results later.