Bi-fold doors

Door size calculator

To calculate the dimensions of the doors or openings we strongly recommend using Centor’s “Doorcalc” program, which is a Microsoft Excel
spreadsheet. To manually calculate door sizing for an opening, follow the following steps:
1 Prepare a basic sketch of your door opening (see worked example), to visualize clearances and check sizes.
2 The calculation is based on all panels being equal width, using half-offset hinges (Patent Pending). Note that the allowance between each panel
is 4mm although hinge thickness is less – this allowance has been determined by consultation with fabricators as the best
approximation for calculation. Clearance between hinges and hinge pins, coupled with the pressure from compression seals accounts
for the allowance being larger than the nominal hinge flap thickness.
3 Recommended clearances are as follows;
• Jamb to panel (door closed) 7mm
• Panel to panel (door closed) 4mm
• Top of panel to head 5mm
• Bottom of panel to sill 10mm for concealed guides
4 Panel width W
Opening width L
Total number of panels N

Panel width is: W = L – 14 – (4 x (N – 1)) **

Worked Examples

Clear opening size 2425 high x 4200 wide (L), and a 3L x 2R arrangement.


W = 4200 – 14 – (4 x (5 – 1))

W = 834 mm

Check against your door layout:

L = 2(7.0) + 4(4) + 5(834) = 4200 (OK)

The panel height is the opening height less the nominal top and bottom clearances: Panel Height H = 2425 – 5 – 10 = 2410mm

Common panel layouts

PS pivot set HHS half offset hinge set
WPS wall pivot set HS hinge set (flat)
ICS intermediate carrier set EH external handle
LCS left carrier set DB dropbolt
RCS right carrier set  
Passage set
Handles / Lock sets refer to Centor Door
Furniture at
Dropbolts top and bottom
Per pair of doors
1 x left carrier set
1 x right carrier set
1 x hinge set
2 x dropbolt

Use one exterior handle on exit door (outward system) where passage
set / lock not required. Use dropbolts top and bottom to lock door from
the inside only.
Note> Exit door not accessible from exterior in this application.

Use one exterior handle on each pair of doors (inward system) to
pull open and close doors