Door Hinges: Quantity, Placement, and Load Capacity
Hinges are the load-bearing foundation for all swinging doors. The calculation focuses on matching the door's weight and size to the hinge's load capacity and ensuring proper placement for stability.
Hinge Quantity Rule
The number of hinges required depends on the door height and weight:
Doors up to 60 inches (1.5m): Minimum of 2 hinges.
Doors 60 to 90 inches (2.3m): Standard requirement is 3 hinges.
Doors over 90 inches or Heavy Doors: Requires 4 hinges or more.
A heavier, fire-rated, or high-usage door (e.g., commercial entrance) may require an additional hinge regardless of height to distribute the increased load and stress.
Hinge Placement (Standard 7-11 Rule)
Proper placement is essential to prevent warping and sagging. The standard rule of thumb for 3-hinge installation is:
Top Hinge: Place 7 inches down from the top of the door frame.
Bottom Hinge: Place 11 inches up from the bottom of the door frame.
Center Hinge: Place exactly midway between the top and bottom hinges.
This maximizes leverage, supporting the weight where it is most concentrated and distributing stress away from the frame.
Cabinet Hinges: Types and Quantity per Door
Cabinet hinges are primarily chosen based on the desired door overlay (how much the door covers the frame) and are almost always concealed (hidden from view when the door is closed). The quantity rule is simpler than for entry doors.
Hinge Quantity Rule for Cabinets
The quantity is determined by door height and weight (e.g., doors with heavy glass inserts require more support):
Doors up to 40 inches (1m): Standard requirement is 2 hinges.
Full Overlay: The door completely covers the cabinet box frame edge, common in modern frameless cabinets.
Partial Overlay: The door partially covers the frame, leaving a small space (reveal) to show the frame, common in framed face-frame cabinets.
Inlay/Inset: The door sits flush inside the cabinet frame opening, requiring specialized hinges that handle the load entirely within the box.
Drawer Slides: Length, Over-Travel, and Weight Rating
Drawer slides are estimated based on the drawer box depth and the required weight capacity, especially critical for deep storage or heavy-duty applications (e.g., filing cabinets, toolboxes).
Slide Length and Over-Travel
Slide Length: Slides are typically purchased in lengths 1 to 2 inches shorter than the actual drawer box depth to allow clearance for the back of the cabinet.
Over-Travel Slides: These specialized slides extend the drawer box past the face of the cabinet, offering 100% access to items stored at the very back. They are essential for deep pantry or utility drawers.
Weight Rating (Dynamic Load)
The slide's published rating (e.g., 75 lbs, 100 lbs, 200 lbs) refers to the **dynamic load**—the maximum weight the slide can support when the drawer is fully extended and loaded. For standard kitchen or bathroom drawers, 75 to 100 lbs is sufficient. For heavy-duty use (e.g., kitchen mixer or utility cabinets), commercial slides rated for 150 lbs or more are required.
Pulls and Knobs: Quantity and Ergonomic Placement
Pulls (handles) and knobs are chosen based on aesthetic style, but their quantity and placement are governed by ergonomic and proportional rules.
Quantity Rules for Cabinetry
Standard Doors: One knob or pull, placed on the edge opposite the hinges.
Extra-Wide Doors (over 36 inches): May require two pulls for better load distribution and aesthetic balance.
Drawers: Drawers up to 24 inches wide use one pull or knob. Drawers over 24 inches wide typically require two pulls, placed symmetrically, to prevent the drawer face from racking when pulled open.
Ergonomic and Aesthetic Placement
Placement ensures the hardware is comfortable to grasp and visually appealing:
Upper Cabinet Doors: Knobs or pulls are typically placed 2-3 inches up from the bottom edge of the door frame.
Lower Cabinet Doors: Placed 2-3 inches down from the top edge of the door frame.
Drawers: Centered horizontally on the drawer face. Vertically, they are centered on the drawer face, or placed on the top third for visual emphasis.
Supplemental Hardware: Catches, Closers, and Dampers
Beyond basic hinges and pulls, specialized hardware is required to control door and drawer movement and enhance quiet operation.
Door Closers and Dampers (Soft-Close)
Door Closers (for entry doors) are hydraulic or spring mechanisms calculated based on the fire rating and the required closing force and speed. For cabinetry, **Dampers** or soft-close slides/hinges slow the final closing arc of the door or drawer, eliminating slamming and reducing wear.
Door Stops and Catches
Door stops prevent damage to the wall, while **Catches** (magnetic, roller, or ball catches) are required for doors or drawers without self-closing mechanisms to ensure they remain fully closed. These are calculated on a one-to-one basis for each item requiring closure.
Conclusion
Hardware calculation is a critical process that balances load-bearing structural requirements with aesthetic ergonomics. For doors, quantity is driven by height and weight, ensuring the hinge system prevents sagging and warping.
For cabinetry, accurate estimation requires selecting the correct **slide weight rating** and determining the **fullness multiplier** for pulls on wide drawers. By adhering to these dimensional and proportional rules, the final hardware selection ensures long-term function, safety, and visual balance.
Frequently Asked Questions
About cabinet hardware planning
Should I use knobs or pulls?
Either works—pulls are common on drawers; knobs on doors.
How do I center handles?
Use a drilling jig; measure twice and test on scrap.
What screw length do I need?
Typically 1" for doors, 1-1/4" for drawers; verify thickness.
How many spares to order?
At least 2–4 extra pieces for future replacement.
Are packs standardized?
Pack sizes vary; enter the exact count per pack.
Do I need two pulls on wide drawers?
Yes for >30" width to avoid sag and provide leverage.
Can I mix finishes?
Keep finishes consistent within a room for cohesion.
What about drilling old holes?
Use backplates or wood filler and refinish as needed.
Are templates universal?
Most jigs are adjustable; always check hole spacing.
What is standard hole spacing?
Common pull center-to-center sizes: 3", 96mm, 128mm.
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