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What Size Self Closing Hinge Do I Need? Measure Your Door and Order the Right Set
To order the right Waterson self-closing hinge, you need three measurements: door thickness, door height, and door weight. Thickness tells you the hinge size, height and weight tell you how many hinges go in the set, and the closing style you want tells you which function to pick. This guide walks you through each step so you can order the correct set the first time.
This guide is for interior and exterior swing doors with full mortise hinges.
What Do You Need to Measure Before You Order?
Grab a tape measure and check these four things. Write them down before you start shopping.
1. Door thickness
Measure the edge of the door, not the frame. Most residential doors are 1-3/8" or 1-3/4". Most commercial doors are 1-3/4", and heavy solid wood or custom doors can be 2-1/4" or more. Thickness decides your hinge size.
2. Door height and width
Measure the full height and width of the door leaf in feet and inches. Height decides how many hinges you need.
3. Door weight
Weight matters as much as height. Check the door manufacturer's spec sheet if you have it. A solid core, fire-rated, or glass-lite door is usually much heavier than a hollow core interior door of the same size.
4. Your existing hinges
If you are replacing hinges, measure the leaf height and width, and look at three details: the corner shape (square or rounded), the screw hole pattern, and whether the door has a fire label on the edge. Matching these lets the new hinge drop into the existing mortise.
Which Hinge Size Fits Your Door Thickness?
Match the hinge size to the door thickness first. Every Waterson K51M hinge is full mortise, stainless steel (Type 304 standard), and non-handed, so one hinge fits both left-hand and right-hand doors.
| Door thickness | Hinge size | Model series | Typical door |
|---|---|---|---|
| 1-3/8" to 1-3/4" | 4" x 4" | K51M-400 | Residential interior, garage entry |
| 1-3/4" | 4.5" x 4.5" | K51M-450 | Commercial doors, offices, corridors |
| 1-3/4" to 2-1/4" | 5" x 5" | K51M-500D | Heavy solid wood and insulated doors |
| 2-1/4" and up | 6" x 6" | K51M-600 | Extra thick estate and custom doors |
How Many Hinges Does Your Door Need?
Next, match the number of hinges to the door height and weight. The number in a Waterson part number is the total number of hinges in the set, so A3 is three hinges and B4 is four.
| Hinges per door | Max door height | Max door weight | Notes |
|---|---|---|---|
| 2 | 6 ft | 150 lbs (68 kg) | Offered in 4.5" x 4.5". Not for fire-rated doors. |
| 3 | 7 ft | 260 lbs (120 kg) | The most common set for standard doors |
| 4 (self closing or soft closing) | 8 ft | 330 lbs (150 kg) | A4 and B4 sets |
| 4 (with hold open) | 8 ft | 260 lbs (120 kg) | C4 and D4 sets |
All ratings are for doors up to 4 ft wide. If your door sits right at the top of a range, go up one hinge. A door at the limit can start to sag slightly over time, and an extra hinge is the simplest way to prevent it. For doors larger or heavier than the table, request a quote and the team will size it for you. For more detail, see how many self-closing hinges your door needs.
Self Closing, Soft Closing, or Hold Open?
The letter in the part number tells you how the door closes.
| Letter | Function | How it feels | Fire-rated doors |
|---|---|---|---|
| A | Self closing (mechanical) | Firm, positive close and latch | Yes, on 3 and 4 hinge sets |
| B | Soft closing (hydraulic hybrid) | Smoother, quieter close | Yes, on 3 and 4 hinge sets |
| C | Self closing + hold open | Stays open near 90°, closes from any other angle | No |
| D | Soft closing + hold open | Quiet close with a hold open position | No |
If your door has a fire label, choose an A or B set with 3 or 4 hinges, and follow NFPA 80 for the number of hinges required. Hold open sets (C and D) are for non-fire-rated doors only. Not sure which closing style you prefer? Read self close vs soft close hinges.
How Do You Read a Waterson Part Number?
Every set follows the same pattern: series, size, function letter, number of hinges. For example:
- K51M-450-B3: full mortise, 4.5" x 4.5", soft closing, 3 hinges. Fits a 1-3/4" commercial door up to 7 ft and 260 lbs.
- K51M-400-A3: full mortise, 4" x 4", self closing, 3 hinges. Fits a residential door up to 7 ft and 260 lbs.
- K51M-600-C3: full mortise, 6" x 6", self closing with hold open, 3 hinges. Fits a 2-1/4" door up to 8 ft and 260 lbs.
Each hinge in a set has its own job, such as closing force, swing speed, or latch speed. Install the full set so the door closes the way it was designed to.
Which Corners, Finish, and Options Should You Choose?
Corner radius
If your existing hinge has rounded corners, match the radius so the new hinge fits the old mortise. Waterson offers 1/4" radius and 5/8" radius corners. If the screw holes on your current hinge are staggered, look at the 5/8" radius zigzag option. To check your corner, see what a 5/8 radius hinge is.
Finish
Five standard finishes are available on stainless steel:
- Satin Stainless Steel (US32D / 630): the bare stainless look
- Flat Black (US19 / 631): powder coated
- Dark Satin Bronze (695): powder coated
- Satin Brass (US4 / 731): physical vapor deposition
Custom finishes are available on request.
Options
- Door stop: 90° (WP01) or 120° (WP02). A 2-hinge set needs one door stop, and a 3 or 4 hinge set needs two.
- 316 marine grade stainless: for coastal, pool, and wet exterior doors.
Quick Order Checklist
- Thickness: picks the hinge size (400, 450, 500D, or 600).
- Height and weight: picks the number of hinges (2, 3, or 4).
- Fire label: if yes, A or B set with 3 or 4 hinges, no hold open.
- Closing style: self closing (A), soft closing (B), or with hold open (C or D).
- Existing hinge: match the corner radius and screw pattern.
- Finish and options: color, door stops, and 316 stainless if needed.
What Are the Most Common Ordering Mistakes?
- Ordering too few hinges. A 7 ft door on a 2-hinge set is over the rating. Count by height and weight, not by how many hinges the door had before.
- Choosing hold open for a fire door. C and D sets are not for fire-rated openings.
- Mixing up corner shapes. A square hinge will not sit flush in a rounded mortise without extra work.
- Forgetting door stops. A 3 or 4 hinge set needs two door stops, not one.
- Opening the door too far. Waterson hinges are designed to operate from 0° to 120°. Swinging beyond that can damage the hinge.
Ready to order?
Shop by size, or send your door details to our team for a project quote.
Shop Door Hinges Request a QuoteOrdering for several doors or a full project? See what door information to send our team so we can recommend the right set.
Self-Closing Hinge Ordering FAQ
Do I need a left-hand or right-hand hinge?
No. Waterson K51M hinges are non-handed, so the same hinge works on left-hand and right-hand doors.
Can I replace just one or two hinges with Waterson hinges?
Install the full set. Each hinge in a Waterson set handles a different function, and the set is rated as a whole.
Will Waterson hinges fit my existing hinge prep?
Waterson hinges conform to the ANSI/BHMA A156.7 standard hinge template. Match the size, corner radius, and screw pattern to your existing hinges for the easiest swap.
What if my door is bigger than the table?
The ratings above cover doors up to 4 ft wide and 8 ft tall. For larger or heavier doors, request a quote and the team will recommend a set.