Pound-Force to Newton Converter

1 lbf is exactly 4.4482216152605 N

The pound-force (lbf) is defined as the force that standard gravity, 9.80665 m/s², exerts on a mass of one pound (0.45359237 kg). Multiply the two and you get 1 lbf = 4.4482216152605 N, which NIST also lists as the exact conversion factor. Going the other way, 1 N is about 0.2248 lbf, so 100 lbf is 444.82 N and 1,000 N is 224.81 lbf.

The converter above handles ten units at once: pound-force and newton, plus kilonewton, kilogram-force, gram-force, tonne-force, kip, ounce-force, dyne and poundal. Type a number in any field and the other nine follow, with a sentence saying what mass that force would weigh. On the spring scale the top ruler is lbf and the bottom is N, so you can see how the two units line up, and the ladder below shows where your value sits among everyday and engineering forces.

When you need to convert

• Reading a US component data sheet: actuators, gas springs and load cells often list force in lbf. To compare them with a metric design that works in N or kgf, convert first. 200 lbf is 889.64 N, or 90.72 kgf.
• Checking kN markings on climbing gear: a 22 kN stamp on a carabiner is 4,945.8 lbf, or 2,243.4 kgf. The UIAA says its standard for climbing carabiners demands a static strength of more than 20 kN.
• Comparing aircraft engine thrust: some manufacturers, GE Aerospace among them, quote thrust in lbf. The 115,300 lbf that GE gives for the GE90-115B at sea level is 512.88 kN.
• Turning body weight into a force for a physics problem: a 50 kg person weighs 490.33 N under standard gravity, which is 110.23 lbf.
• Cleaning up old kgf-based documents: spring, scale and dynamometer sheets that give a force in kgf, or just in "kg", become newtons when you multiply by 9.80665.

How to use it

1. Type the value you know into the matching field. The two large fields are pound-force (lbf) and newton (N); the eight below are kN, kgf, gf, tf, kip, ozf, dyn and pdl. A thousands comma such as 1,234.5 is fine.
2. The field you typed in becomes the reference (dark outline) and the other nine update. If any value is rounded, the "=" between the two large fields turns into "≈".
3. Under "Decimals" choose 0, 1, 2, 4 or 6. The line under the fields shows the full exact value when it terminates, or six decimals when it does not, and the line below that says what mass that force would weigh.
4. Drag the spring scale, or focus it and press ← and → (PgUp and PgDn move 10 steps). Near the end of the scale the range widens in steps of 1, 2 and 5, and it narrows again for smaller values.
5. Tap a row in "How big is this force?" to put that value in the fields above. "Copy result" copies all ten values, and "Copy link" puts your current input in the address.

How it is calculated

Every unit is first converted to newtons, then divided by the number of newtons in the target unit. The table lists each unit's value in newtons. Values marked exact come straight from the definitions and terminate; the others are cut at eight decimals and end with an ellipsis.

1. lbf to N: lbf × 4.4482216152605 (100 lbf is 444.82 N)
2. N to lbf: N ÷ 4.4482216152605, which is N × 0.2248089… (1,000 N is 224.81 lbf)
3. kgf to N: kgf × 9.80665 (70 kgf is 686.47 N)
4. lbf to kgf: lbf × 0.45359237 (100 lbf is 45.36 kgf). Both units use the same standard gravity, so the lbf-to-kgf ratio equals the lb-to-kg ratio.
5. lbf to pdl: 1 lbf is 32.174049 pdl, which is standard gravity expressed in feet per second squared (32.174049 ft/s²).

The converter keeps every factor as an exact fraction and rounds only once, at the end. That is why 1,000 lbf comes out as exactly 4,448.2216152605 N, and why the fields show only the value rounded to the decimals you picked.

lbf, N and kN conversion tables

Pound-force converted to newtons and kilograms-force (rounded to two decimals).

Newtons converted to pound-force, kilogram-force and the mass in grams that would weigh that much (lbf and kgf to four decimals).

Kilonewtons, the unit most gear and structural data use (one decimal).

lb vs lbf, kg vs kgf, and N

The pound (lb) and kilogram (kg) are units of mass; lbf, kgf and N are units of force. Mass is how much matter an object has and does not change from place to place. Weight is the force gravity puts on that mass, so it changes when gravity does. lbf and kgf are defined as the weight under standard gravity, which is why a 1 lb object weighs 1 lbf and a 1 kg object weighs 1 kgf there.

• How many grams is 1 N? A newton is a force, so it cannot equal a mass in grams. Under standard gravity, though, an object of 101.97 g weighs 1 N, so "1 N is about the weight of 102 g" is a handy rule. 100 N is the weight of about 10.2 kg.
• Is 1 kg the same as 10 N? A 1 kg object weighs 9.80665 N. Using 10 N is a rounding that makes mental arithmetic easier, and it is about 2% too high.
• What does a 150 lb person weigh in newtons? Under standard gravity that is 150 lbf, or 667.23 N. A bathroom or luggage scale really measures a push or pull and then displays it as kg or lb.
• lbm and lbf: engineering documents write lbm for the pound of mass and lbf for the pound of force. When only "lb" is written, you have to tell from context whether it means mass or force.

Reading force on a spring scale

Within its elastic limit a spring stretches in proportion to the force pulling on it, so marking the stretch gives you a force gauge. The scale in the converter is one spring with two rulers. Read the top ruler (lbf) and the bottom ruler (N) at the pointer and the ratio is visible: 100 lbf lands near 444.8 N. When the value changes, the spring stretches to its new length and settles after a small bounce, much like a real scale with a weight hung on it.

The ladder below runs from 1 N up to rocket thrust on a logarithmic bar. 1 N and 7,700,000 lbf (about 34.25 MN) differ by more than seven orders of magnitude, which an ordinary linear scale cannot show in one picture. Your value appears as an orange "Your value" row, slotted in between the reference forces.

Reading gear and engine ratings

Large forces such as thrust are easier to read in kN or MN. The GE90-115B figure is 512.88 kN, which is the weight of an object of about 52,299 kg under standard gravity.

Where pounds-force are still used

The kip, short for kilopound, is 1,000 lbf, or 4,448.2216152605 N according to the NIST factor. In the United States it is a common unit for structural loads, because a building or bridge load of 50,000 lbf is easier to write as 50 kip. If you work from US structural drawings and need kN, multiply by 4.448.

Aircraft engine thrust is another place where lbf survives. GE Aerospace lists the GE90-115B at 115,300 lbf of maximum power at sea level. Dividing by 224.8 gives about 512.9 kN for anyone who compares engines in SI.

Finally, US technical texts keep mass and force apart with lbm and lbf. In those books a "pound" with no suffix can mean either, so check the equations: if the pound is multiplied by an acceleration, it is mass.

What happens when units get mixed

In 1999 NASA's Mars Climate Orbiter was lost as it approached Mars. The mishap investigation board's report names the root cause: a ground software file called "Small Forces" produced its output in pound-force seconds (lbf·s) instead of newton seconds (N·s), and the navigation software expected the latter. Since 1 lbf·s is 4.448 N·s, the receiving side used numbers about 4.45 times too small.

Common mistakes

• Rounding the factor to 4.45: that is about 0.04% above the exact value and adds 1.78 N for every 1,000 lbf. For large loads, use 4.4482216152605.
• Treating 1 kg as 10 N: roughly right, but about 2% high. For tests and design values use 9.80665.
• A force written in "kg": the kg printed on a grip dynamometer or spring balance usually means kgf. Multiply that number by 9.80665 to get newtons.
• Mixing up tons-force: the metric tonne-force (tf) is 1,000 kgf, or 9,806.65 N, while NIST's ton-force (2,000 lbf) is 8,896.443230521 N. Both are called a "ton", yet the metric one is about 10% larger.
• Torque is not force: lbf·ft and N·m are torque, which is force times distance, so this converter cannot convert them. Use a torque converter instead.

Limits

• kgf, gf, tf, lbf, ozf and kip are all computed with standard gravity, 9.80665 m/s². Real gravity varies a little with latitude and altitude, so a scale at your location can read slightly differently.
• The tool handles the size of a force, not its direction. You can enter values from 0 up to 100,000,000 N (100 MN, about 22.48 million lbf).
• The gear and engine values on the ladder come from the sources below and manufacturer pages. For a real product, check the rating printed on it and in its manual.
• Calculations happen only in your browser and nothing is sent anywhere. "Copy link" puts your input into the address.

Basis: the factors come from NIST SP 811 Appendix B.8 and its footnotes and are definitions, so they do not change from year to year. The NASA, UIAA and GE Aerospace pages were checked against the originals on October 21, 2026.

Sources

• 01NIST SP 811 Appendix B.8: Factors for units listed alphabeticallydyne 1.0 E-05 N, kilogram-force 9.806 65 N, kip 4.448 222 E+03 N, ounce-force 2.780 139 E-01 N, pound-force 4.448 222 N, poundal 1.382 550 E-01 N, ton-force (2000 lbf) 8.896 443 E+03 N
• 02NIST SP 811 Appendix B footnotesExact pound factor 0.453 592 37 kg; with g_n = 9.806 65 m/s², the exact lbf factor is 4.448 221 615 260 5 N
• 03NASA: Mars Climate Orbiter Mishap Investigation Board Phase I Report (1999)The "Small Forces" ground software output lbf·s instead of N·s, named as the root cause
• 04UIAA: How strong are your karabiners?UIAA standard for climbing karabiners: static strength of more than 20 kN (about 2 tonnes of mass)
• 05UIAA 110 Explanatory Note (2025)UIAA 101 comparison: single rope impact force at most 12 kN, half rope at most 8 kN
• 06GE Aerospace: GE90GE90-115B maximum power at sea level, 115,300 lbf
• 07NASA: Saturn V Stage 1Five F-1 engines, "nearly 7.7 million pounds of thrust"

Frequently asked questions

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