How this calculator works
The name lbs to psi hides an important gap: a pound is a force, while psi already divides by area. The useful conversion behind this search is pounds-force per square foot, written psf, to pounds-force per square inch, or psi. One square foot contains 144 square inches, so the same force spread over a square foot produces one 144th of the pressure it would produce on a square inch. That makes the conversion an exact division by 144.
Formula
psi = psf / 144. psf = psi x 144. The 144 comes from 12 inches by 12 inches in one square foot. In pascals, 1 psf = 47.8802589803 Pa and 1 psi = 6,894.757293168 Pa.
Worked example
144 psf = 1 psi. 100 psf = 0.694444 psi. 1,000 psf = 6.94444 psi. 2,000 psf = 13.8889 psi. 50 psf = 0.347222 psi.
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Frequently asked questions
Can pounds be converted directly to psi?
No. A pound is a force and psi is a force per area. To get a pressure you also need the area the force acts on, or you need the pressure expressed per square foot, which is what this page converts.
Why is the factor 144?
A square foot has 12 inches on each side, so it holds 12 x 12 = 144 square inches. Spreading the same force over the larger area gives a pressure 144 times smaller.
Where are psf values used?
Structural loading tables use psf for floor live loads, roof loads and wind pressures. For example, a residential floor live load is often specified around 40 psf, and wind uplift can reach much higher values.
Is this the same as pound-force per square inch?
Yes. The psi in this page is pounds-force per square inch, the standard US pressure unit. The psf value is the matching pounds-force per square foot, which is why both appear on structural drawings.