Firestop Penetration Calculator

Annular space is floored at zero because a physical gap can never be negative — the engine subtracts the penetrant's combined area from the opening's area and stops at zero if that subtraction would go negative. Fill ratio has no such floor or ceiling; it keeps rising past 100% to show just how much larger the penetrant is than the opening, which is the calculator's way of flagging that the two dimensions you entered don't physically fit together.

Each additional penetrant subtracts its own circular area from the opening, so the combined penetrant area scales directly with count — five 2-inch pipes occupy exactly five times the area of one. That combined area is what's subtracted from the opening area to get annular space, so more penetrants at a fixed opening size shrink the annular space (and can drive it to zero) even if no single pipe is larger than the opening.

No. Annular space is pure two-dimensional circle geometry — opening area minus penetrant area — and never references wall thickness. Thickness only enters afterward, as the depth multiplied against annular space to get Sealant volume, so a thicker wall raises the sealant estimate without changing the annular space figure itself.

The engine multiplies the raw annular-space-times-thickness volume by 1.1 before converting to fluid ounces, an allowance for tooling waste and imperfect gun dispensing on real installations. It's a fixed 10% regardless of opening size, penetrant count, or wall thickness — it does not grow or shrink with the geometry.