Four answers, not one
Ask how many business cards come off a 12.5 by 19 press sheet and the honest reply is a question about the press. Half an inch of gripper comes off one edge and nothing images there, and a quarter inch of trim and colour bar comes off the other three. Grip a width edge and the imageable area is 12 by 18.25; grip a height edge and it is 11.75 by 18.5. Those are close in area and nowhere near equal in what they hold.
Run a 3.5 by 2 card through all four combinations and you get 27, 30, 27 and 25 up. The winner is gripper on a width edge with the card turned — six across by five down. The loser is gripper on a height edge with the card turned, which is the same rotation that won in the other feed direction. That is the trap: rotating the piece helped in one case and hurt in the other, and no rule of thumb gets that right.
The gripper is why the arithmetic is lopsided
If the sheet lost the same margin all round, the two feed directions would be identical and there would be two answers rather than four. The gripper breaks the symmetry — it is taken off exactly one edge, so the sheet has a long axis and a short axis that behave differently, and which one you feed changes both usable dimensions at once. Sheet nesting calculators built for plywood or acrylic assume a symmetric margin and will give you the wrong number here, usually the optimistic one.
Butt cuts and separate trims
On the default settings the cards butt against each other: one knife cut serves both neighbours, the bleed on the two pieces overlaps, and the pitch is the card size exactly. Switch to separate trims and each card carries its own bleed on both sides plus a knife allowance, so the pitch grows from 3.5 by 2 to 3.875 by 2.375 and the count drops. That is the real cost of a job that cannot be butt cut — a die-cut shape, a piece with a score too close to the edge, anything where the guillotine has to drop a strip between neighbours.
Parent, press sheet, piece
Paper arrives as a parent — 25 by 38 for text stock, 20 by 26 for cover — and gets cut down before it ever sees the press. Two steps of division, and both round down. A 25 by 38 parent gives four 12.5 by 19 press sheets with nothing left over, which is a clean cut and not the usual case; try 23 by 35 into the same press sheet and you get one, with most of the parent in the bin.
Multiply the two and the default job comes out at 120 cards per parent sheet. Twenty-five hundred cards with 5 percent spoilage is 2,625 pieces, 88 press sheets, 22 parents. At 42 cents a parent that is 9.24 dollars of paper, which is 3.70 dollars a thousand cards — worth knowing before anybody argues about the ink.
Where this is optimistic and where it is not
It is a plain grid of one repeated piece. A shop imposing for real will gang several jobs on one form, tuck small pieces into the trim, and work the sheet and turn to get both sides off one plate set. All of those beat this number. What it will not beat is the geometry: the gripper is real, the trim is real, and the four-way comparison holds however clever the imposition gets.
Questions people ask
How many business cards fit on a press sheet?
On a 12.5 by 19 press sheet with a half inch gripper and a quarter inch trim, a 3.5 by 2 card butt cut comes out 30 up — six across by five down, with the card turned so its short dimension runs across the sheet. The other three combinations of feed edge and card rotation give 27, 27 and 25. Change the sheet or the gripper and the ranking changes with it.
Why does the gripper edge change the count?
Because it is taken off one edge only. A symmetric margin would leave the two feed directions equivalent, but a gripper on one edge shortens one dimension by the gripper plus one trim and the other by two trims, so the imageable rectangle is a different shape depending on which way the sheet goes through. That is why the page prints four layouts instead of two.
Do butt cuts really save that much?
On small pieces, yes. A 3.5 by 2 card butt cut has a pitch of 3.5 by 2. Give every card its own bleed and a knife allowance and the pitch becomes 3.875 by 2.375, which is 33 percent more area per card. The count falls from 30 up to fewer, and on a long run that is the difference between one skid of paper and two.
What gripper and trim allowance should I use?
Whatever your press and your finishing actually need, which is a question for the person who runs them. The fields default to half an inch and a quarter inch as placeholders, not as facts about presses. A small format duplicator, a half-size offset press and a production digital press all grip differently, and a job carrying a colour bar needs more room than one that is not.
Does this account for ganging several jobs on one sheet?
No. It repeats one piece in a rectangular grid, which is the conservative case. A shop that gangs work will fit more, because the leftover strip that is useless for your card may be exactly the size of somebody else's reply card. Use this to check a quote and to compare sheet sizes, not to tell an imposition operator what is possible.