Convert Poundals to Newtons

A poundal (pdl) is a non-SI unit of force used in the foot-pound-second (FPS) system. A newton (N) is the SI unit of force. To convert poundals to newtons, use a fixed conversion factor.

• Conversion factor: 1 pdl = 0.138255 N
• Formula: N = pdl × 0.138255
• Reverse check (optional): 1 N = 7.23301 pdl

Example:

• 25 pdl × 0.138255 = 3.456375 N
  So, 25 poundals = 3.456 N (rounded to three decimals).

For clean results, keep extra digits while you calculate, then round at the end.

What is a poundal (pdl)?

A poundal (pdl) is a unit of force from the foot-pound-second (FPS) system. It’s defined as the force needed to accelerate a 1-pound mass at 1 foot per second squared (1 ft/s²). You’ll mainly see poundals in older texts and some engineering problems.

What is a newton (N)?

A newton (N) is the SI unit of force. One newton is the force needed to accelerate a 1-kilogram mass at 1 meter per second squared (1 m/s²). It’s the standard force unit used in science and most engineering work today.

What is the conversion from poundals to newtons?

The direct conversion is:

• 1 poundal (pdl) = 0.138255 newtons (N)
• 1 newton (N) = 7.23301 poundals (pdl)

These values come from the exact definitions of the foot, pound, and meter.

How do you convert poundals to newtons?

Use this formula:

• Newtons = Poundals × 0.138255

Example:

• 50 pdl × 0.138255 = 6.91275 N

For most uses, rounding to 6.91 N is fine.

How do you convert newtons to poundals?

Use the inverse formula:

• Poundals = Newtons × 7.23301

Example:

• 10 N × 7.23301 = 72.3301 pdl

You can round based on how precise your input data is.

Why does a poundal convert to a smaller number of newtons?

A poundal is based on feet, pounds, and seconds, while a newton is based on meters, kilograms, and seconds. The size of the base units differs, so the force unit size differs too. Since the newton is a larger unit of force than the poundal, the value in newtons is smaller for the same force.

Are poundals the same as pound-force (lbf)?

No. A poundal (pdl) and a pound-force (lbf) are different units.

• Pound-force (lbf) is tied to Earth’s gravity (weight).
• Poundal (pdl) is tied to mass and acceleration in FPS units.

A common relationship is:

• 1 lbf = 32.174 pdl (approx.)

When would you use poundals instead of newtons?

You might use poundals when working with older physics or engineering problems written in the FPS system. They can also show up in exercises that focus on unit systems and how force relates to mass and acceleration.

What’s a quick mental estimate for converting poundals to newtons?

For a fast estimate:

• 1 pdl is about 0.14 N
• N is about pdl divided by 7

Example:

• 70 pdl ≈ 70 ÷ 7 = 10 N (close to the exact value of 9.68 N)

How many significant figures should you use for pdl to N conversions?

Match the precision of your starting value.

• If your input is 2 significant figures, keep about 2 significant figures in the result.
• If your input is measured data, don’t add extra digits that suggest more accuracy than you have.

Example:

• 12 pdl (2 sig figs) → 12 × 0.138255 = 1.65906 N → 1.7 N

Can poundals be used in Newton’s second law (F = ma)?

Yes. Poundals were built for it. In FPS units:

• Force in pdl
• Mass in lbm (pound-mass)
• Acceleration in ft/s²

So F (pdl) = m (lbm) × a (ft/s²) works directly without gravity constants.

What’s a common mistake when converting poundals to newtons?

Mixing up poundals with pound-force is the most common issue. Another common error is using the wrong conversion direction. Always check that:

• pdl to N uses × 0.138255
• N to pdl uses × 7.23301

Is the poundal still used today?

It’s rarely used in modern work. Most fields use newtons, pound-force, or other current standards. Poundals mainly appear in older materials and unit-conversion practice.