Weight Calculator
Weight is the force gravity puts on a mass. Enter a mass and a gravitational acceleration, and this calculator gives the weight in newtons, pounds-force and kilograms-force. It also works backward, from a weight to the mass.
Pick a place or type your own g.
Weight in newtons (N)
686.466
Weight in pounds-force (lbf)
154.324
Weight in kilograms-force (kgf)
70
Pick a place or type your own g.
Mass in kilograms (kg)
70
Mass in grams (g)
70,000
Mass in pounds (lb)
154.324
Mass in ounces (oz)
2,469.18
Conversions use the exact definitions: 1 lb = 0.45359237 kg, 1 oz = 1/16 lb, 1 kgf = 9.80665 N and 1 lbf = 4.4482216152605 N. Results are rounded to six significant figures. A result with more than six digits before the decimal point is rounded to the whole number.
Standard gravity, 9.80665 m/s², is the exact value in NIST's table of constants. The other presets are the Gravity row of NASA's Planetary Fact Sheet, which gives one decimal. NASA states it at the equator, and at the 1 bar pressure level for Jupiter, Saturn, Uranus and Neptune. Both pages were opened on October 14, 2026.
How to use the Weight Calculator
- Choose a mode. "Weight from mass" turns a mass into a force. "Mass from weight" goes the other way.
- For a weight, type the mass and pick its unit: kilograms, grams, pounds or ounces.
- Pick a place to fill in its gravitational acceleration g, or type your own g in m/s². The list has Earth at standard gravity, the Moon, the other seven planets and Pluto.
- Read the weight in newtons, pounds-force and kilograms-force. The results update as you type, so there is no button to press.
- For a mass, switch the mode, type the weight in newtons, pounds-force or kilograms-force, and set the g it was measured under. The calculator shows the mass in kilograms, grams, pounds and ounces.
The weight formula
W = m × g m = W ÷ g
W is the weight in newtons, m is the mass in kilograms and g is the gravitational acceleration in m/s². In this formula the mass belongs to the object and g belongs to the place. Move the object and m stays the same, while g changes and the weight changes with it. The calculator converts the mass to kilograms, multiplies by g and converts the newtons. It uses the exact definitions 1 lb = 0.45359237 kg, 1 oz = 1/16 lb, 1 kgf = 9.80665 N and 1 lbf = 4.4482216152605 N. Each result is rounded to six significant figures, or to the whole number when it has more than six digits before the decimal point. A weight above 10^18 N or under 10^-18 N, or a mass past 10^18 kg or under 10^-18 kg, gets a message, because it comes from a mistyped field.
Worked example
The fields start with these numbers, so you can check each result. A mass of 70 kg at standard gravity, 9.80665 m/s², gives W = 70 × 9.80665 = 686.4655 N. The calculator shows 686.466 N, 154.324 lbf and 70 kgf. Pick the Moon and g becomes 1.6 m/s². The same 70 kg now weighs 112 N, 25.1786 lbf and 11.4208 kgf. Going back, a weight of 686.4655 N at standard gravity is a mass of 70 kg, which is 70,000 g, 154.324 lb and 2,469.18 oz.
Frequently asked questions
What is the difference between mass and weight?
Mass is the m in W = m × g. It is a property of the object, measured in kilograms. Weight is the W, the force gravity puts on that mass, measured in newtons. A 70 kg mass is 70 kg at standard gravity and at the Moon's 1.6 m/s². Its weight is 686.466 N in the first case and 112 N in the second.
My scale shows kilograms or pounds. Is that a weight?
In everyday speech, yes. NIST's Guide to the SI, section 8.3, says that in commercial and everyday use weight usually means mass, and its unit is then the kilogram. In science, weight is a force in newtons, and that is the meaning this calculator uses. To get the force, enter the scale reading as the mass.
What is a kilogram-force?
One kilogram-force is 9.80665 N, the weight of one kilogram at standard gravity. That is why 70 kg at standard gravity weighs 70 kgf. With any other g the two numbers differ. At the Moon's 1.6 m/s², 70 kg weighs 11.4208 kgf.
Where do the g values in the list come from?
Standard gravity, 9.80665 m/s², is the exact value NIST lists as the standard acceleration of gravity. The values for the Moon, the planets and Pluto are the Gravity row of NASA's Planetary Fact Sheet, which gives one decimal, such as 1.6 for the Moon, 3.7 for Mars and 23.1 for Jupiter. NASA states it at the equator, and at the 1 bar pressure level for the gas giants. Both pages were opened on October 14, 2026. If you have a more exact g, type it in.
Is g 9.80665 m/s² everywhere on Earth?
No. 9.80665 m/s² is a fixed standard value, not a measurement of where you are. NASA's Mars fact sheet lists Earth's surface acceleration as 9.78 m/s² at the equator and 9.83 m/s² at the poles. If you know the g of your location, type it into the g field.