When to use: Select an electromagnetic lock holding force from the door leaf weight, width, and required security level. Standard ratings are 300, 600, 1200, 1500 and 2000 lbf. IBC egress note: mag-locks on egress doors must release per IBC 1010.2.11/1010.2.13 — sensor-release (motion + manual) or door-hardware-release with a listed device, loss of power releases the lock, and signage is required.
This calculator helps engineers select the correct electromagnetic lock holding force for a door based on door leaf weight, width, and the required security level. Standard maglock ratings of 300, 600, 1200, 1500, and 2000 lbf correspond to different installation scenarios from interior office doors to high-security perimeter entries.
An electromagnetic lock generates holding force through the magnetic attraction between an armature plate attached to the door and an electromagnet mounted on the frame. The minimum required holding force must resist forced entry attempts while accounting for the mechanical leverage applied at the strike point relative to the hinge axis.
Wider doors experience higher torque at the lock for the same applied force — a person pushing on a 36-inch door at the handle applies more torque to the lock than on a 30-inch door. The door weight affects the impact and dynamic forces applied during forced entry attempts. Security level multipliers reflect the expected threat profile: 1.0× for standard interior applications, 1.5× for perimeter doors, and 2.0× for detention or high-security installations.
Standard commercial maglocks are rated at 300 lbf (small interior doors), 600 lbf (standard single door, most common), 1200 lbf (heavy double doors or high security), 1500 lbf, and 2000 lbf (maximum security applications).
ANSI/BHMA A156.23 specifies test methods and performance requirements for electromagnetic locks including holding force testing. IBC Section 1010.2.13 (sensor release) and 1010.2.11 (door-hardware release) govern egress requirements for maglocks — specifically that maglocks on egress doors must release on approach, release via hardware, and release on loss of power. NFPA 101 §7.2.1 mandates free egress and requires fire alarm integration for maglock release. UL 294 covers access control system listings that include electromagnetic locking hardware.
All maglocks on egress doors must be fail-safe — they release when power is removed. This is mandatory under IBC egress requirements and NFPA 101. Never install a fail-secure maglock on an egress path. Required release methods include: automatic release via a request-to-exit (REX) motion sensor covering the egress side, a green "PUSH TO EXIT" button, release via the fire alarm system, and loss of building power.
The holding force selected must also account for door closer force, wind pressure (for exterior doors), and the accumulated residual magnetism that can cause the armature to stick briefly after de-energization — specify maglocks with active hold-off delay or time-delay release for high-traffic doors. Coordinate holding force with the door frame and mounting hardware load ratings.
Enter the door leaf weight in pounds, the door width in inches, and select the security level appropriate for the installation. The tool calculates the minimum required holding force using a leverage-adjusted formula and selects the next standard maglock rating that meets or exceeds the requirement. Use the recommended lbf value to specify the maglock in the hardware schedule. Always verify the selected product's current draw with the Card Reader Current Draw calculator to ensure the PSU is adequately sized.
A 600 lbf single-door maglock is the most common specification for standard interior and perimeter single doors with moderate security requirements. This corresponds to approximately 272 kg of holding force, which resists typical forced entry attempts on a standard hollow metal door frame.
Yes, under IBC 1010.2.13 (sensor release) — the maglock must release automatically when a person approaches the egress side (PIR/REX sensor), must release when the fire alarm activates, and must release on loss of power (fail-safe). A "PUSH TO EXIT" button may also be required. Confirm with the Authority Having Jurisdiction (AHJ).
A standard 600 lbf maglock draws approximately 400–500 mA at 12 VDC (approximately 5–6 W) continuously while energized. At 24 VDC the current is approximately 200–250 mA for the same power. Verify against the manufacturer datasheet for the specific product.
Double-door maglocks are rated at 1200 lbf or higher and mount at the meeting stile (center) of a pair of doors. Each leaf has its own armature plate. They require careful alignment during installation. A 1200 lbf double-door unit uses approximately double the current of a 600 lbf single unit.
Residual magnetism is the magnetic field that remains in the armature and electromagnet core briefly after power is removed, causing the door to stick momentarily. Specify maglocks with a built-in time-delay hold-off circuit (typically 100–500 ms) that briefly reverses the magnetic field to release residual flux before the door can be opened. This is important for high-traffic applications.
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