Torque, arm, force
A closer resists in torque — pounds times inches about the hinge pivot. Divide by the distance from that pivot to your hand and you have the force you feel. The whole page is that one division, and the only part worth being careful about is which edge the arm is measured from.
It is the hinge pivot, not the hinge edge of the leaf and not the frame. On a 36 inch leaf with the pivot sitting a quarter inch outside the hinge face, the leading edge is 36-1/4 inches out. A hand on that edge working against 110 lb-in of closer plus 2 lb of seal drag feels 5.0 lb. Measure the arm from the wrong edge and the answer inverts in the direction that matters — a wider door reads harder instead of easier.
The push point is the variable nobody records
Run the default numbers along the leaf and the same door goes 5.0 lb at the edge, 5.5 lb three inches in, 6.0 lb six inches in and 7.4 lb a foot in. That is a 48 percent swing across a hand span, on hardware nobody touched. Any force figure quoted without saying where it was taken is missing half the measurement.
Narrow leaves are the ones people complain about
Move the same closer at the same setting onto a 30 inch leaf and the edge force goes from 5.0 lb to 5.9 lb. Nothing about the spring changed; the arm got six inches shorter. This is the reason a closer that felt fine on the main entry feels wrong on the narrow office door down the corridor, and the reason swapping closers between openings to solve a complaint often just moves it.
Seals work the other way round, slightly. Seal drag is a force at the leading edge, so it scales with the arm and mostly cancels — the closer spring is the term that does not, and it is the one that dominates the difference.
What sits outside the arithmetic
Closer torque is not one number. It builds through the swing, backcheck can put a wall in near the end, and the sweep and latch valves change the return without changing the opening. The form takes two readings so the shape is at least bracketed, but the chart from the closer manufacturer is the authority on it, and a gauge on the actual leaf beats both.
Everything about whether a given opening is allowed to be a given force — and whether a fire door with a self-closing device is treated differently — is code and listing territory, decided by the authority having jurisdiction and the door hardware consultant. This page restates the figure you give it and does no judging. For what the leaf itself weighs, the door slab weight calculator works it from the core; for the arc the leaf sweeps once it opens, the door swing clearance calculator.
Questions people ask
How do I turn a closer size into pounds of push?
You cannot go straight from a size number — a size is an index into a manufacturer chart, and the chart is what gives a torque. Read the torque for your size, spring setting and opening angle off that chart, put it in the form, and divide by the arm from the hinge pivot to your hand. The form does the division and prints the arm it used so you can check it.
Where is the arm measured from?
The hinge pivot, which sits slightly outside the hinge face of the leaf. On a 36 inch leaf with a quarter inch pivot offset, the arm to the leading edge is 36-1/4 inches, and the arm to a hand six inches in from that edge is 30-1/4. Measuring from the frame or from the hinge edge of the slab gives an arm that is wrong by a small amount at the edge and wrong by a lot near the hinge.
Why is a narrow door harder to open with the same closer?
Shorter arm. At 110 lb-in of closer with 2 lb of seal drag, the edge of a 36 inch leaf takes 5.0 lb and the edge of a 30 inch leaf takes 5.9 lb — an 18 percent increase for six inches of width. The spring is identical; the leverage is not. It is the single most common reason one door in a building feels wrong when the rest are fine.
Does this tell me whether the door meets the opening force requirement?
No, and it will not. If you enter the figure your guidance gives, the page restates it and converts it to a torque at your arm so you can see what it corresponds to. Whether that figure applies to this opening, where it is measured, and what a fire-rated door with a closer is required to do are questions for the authority having jurisdiction and the hardware consultant. Nothing here is a compliance statement.
Why does the measured force not match the calculation?
Usually something the arithmetic cannot see: a bent arm, a dry or binding hinge, the leaf rubbing the stop, a frame out of plumb, or a pressure difference across the opening from the ventilation. A gauge hooked on the leading edge settles it faster than any recalculation, and if the gauge and the chart disagree by a lot, the hardware is telling you something.