Framing & structure
Joist hanger & connector schedule
Count joist hangers and fasteners for every ledger, beam and header, and check each hanger's reaction against its catalogue rating.
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What the joist hanger calculator works out
A joist hanger calculator counts the hangers and fasteners a floor or deck needs and checks the load on each one. Add a row for every ledger, beam or header, with the joist size, the joist span and the length of header the joists frame into, and it returns the hangers by size, the header and joist fastener totals with an allowance, and the reaction each hanger must carry.
Joist counts come from the header run and the spacing: the run divided by the spacing, rounded up, plus one, so no gap is wider than the spacing. A 16 ft ledger with joists at 16 in centres takes 13 hangers. The reaction is the load on half a joist span: at 50 psf, 16 in centres and a 12 ft span, each hanger carries 400 lb.
Hanger ratings and fastener schedules depend on the exact model, the fasteners used, the species and the load duration, so the calculator uses the values you enter from the manufacturer's catalogue rather than a product table. It does not check the header, skewed or sloped hangers, or uplift, and the catalogue's installation instructions govern.
How to use the joist hanger & connector schedule
- Choose Imperial or Metric. Imperial is the default, and your choice carries across the free tools.
- Choose the Hanger type, enter the Joist spacing and the Dead load and Live load the joists carry.
- Enter the Header fasteners per hanger and Joist fasteners per hanger from the catalogue's fastener schedule, and a Fastener allowance (%) for drops and spares.
- Add a row for each header: a Location name, the Joist size, Plies for doubled joists, the Joist span, the Header run, and Joists (0 = from run) to count from the run or enter a count. Set Hung ends to Both ends for joists hung at each end, and enter the Allowable load per hanger from the catalogue.
- Read the hanger count by size, the fastener totals, the largest reaction and any row over its rating, then download the schedule as a PDF or CSV for the order.
Worked example
Imperial: A 16 ft ledger and a 3 ft stair header at 16 in centres take 13 + 4 = 17 hangers; at 10 + 40 psf on a 12 ft joist span each ledger hanger carries 400 lbf, 44% of a 900 lbf catalogue rating.
Metric: A 4.8 m ledger and a 0.9 m stair header at 400 mm centres take 13 + 4 = 17 hangers; at 0.5 + 2.0 kPa on a 3.6 m joist span each ledger hanger carries 1.8 kN, 45% of a 4 kN catalogue rating.
How many joist hangers do I need?
One hanger for each joist end that frames into a ledger, beam or header instead of bearing on top of it. For a run of header, the count is the run divided by the spacing, rounded up, plus one for the first joist. Joists hung at both ends, such as joists between two beams, need two hangers each.
| Header run | 12 in centres | 16 in centres | 24 in centres |
|---|---|---|---|
| 8 ft | 9 | 7 | 5 |
| 10 ft | 11 | 9 | 6 |
| 12 ft | 13 | 10 | 7 |
| 16 ft | 17 | 13 | 9 |
| 20 ft | 21 | 16 | 11 |
Joist hanger load: the reaction at each end
For a uniformly loaded joist on a simple span, each end carries half the load: reaction = (dead + live) × spacing × span ÷ 2. The table uses 10 psf dead and 40 psf live, typical for residential floors and decks. Compare each value with the allowable load the catalogue lists for the hanger, its fasteners and the load duration.
Doubled members that carry a header, a stair stringer or a point load need their own reaction; the spacing-based reaction does not cover them.
| Joist span | 12 in centres | 16 in centres | 24 in centres |
|---|---|---|---|
| 8 ft | 200 | 267 | 400 |
| 10 ft | 250 | 333 | 500 |
| 12 ft | 300 | 400 | 600 |
| 14 ft | 350 | 467 | 700 |
| 16 ft | 400 | 533 | 800 |
Face-mount, top-flange and concealed-flange hangers
The hanger type changes how the load reaches the header and how many fasteners it needs. Face-mount hangers are nailed or screwed to the face of the header and are the most common for ledgers and flush beams. Top-flange hangers hook over the top of the header and transfer load by bearing, which suits engineered headers and reduces the face nailing. Concealed-flange hangers turn their flanges inwards for joists at the end of a header or where the flanges must not show.
| Type | Typical use | What to check |
|---|---|---|
| Face-mount | Deck ledgers, flush beams, stair openings | Header thickness for the nail length; every hole filled as specified |
| Top-flange | Engineered headers, steel beams, heavy loads | Top flange bearing and whether the subfloor needs notching |
| Concealed-flange | End of a header, exposed framing | Joist width and the reduced nailing area |
| Double or triple width | Doubled joists, trimmers and girders | Width matches the plies; reaction from the actual load |
Fasteners: use the catalogue schedule
A hanger's rating assumes the exact fasteners in its catalogue entry, in every specified hole. Shorter nails, drywall or deck screws, or empty holes reduce the capacity sharply, and many failures trace back to the wrong fastener. Some hangers list a reduced rating for fewer or shorter fasteners, for example when nailing into a 1½ in ledger.
Preservative-treated lumber corrodes standard galvanizing. Use hangers and fasteners with heavier hot-dip galvanizing or stainless steel as the treatment and the manufacturer require, and never mix stainless and galvanized parts in one connection. The calculator multiplies the per-hanger fastener counts you enter and adds the allowance to give an order quantity.
Worked example: a deck ledger and a stair opening
A deck has a 16 ft ledger with 2x10 joists at 16 in centres spanning 12 ft, and a 3 ft header at the stair opening carrying 6 ft tail joists. The ledger takes 192 ÷ 16 = 12, plus one, so 13 joists; the stair header takes 36 ÷ 16 = 2.25, rounded up to 3, plus one, so 4. That is 17 face-mount hangers for 2x10.
At 10 header and 4 joist fasteners per hanger, the order is 170 and 68 fasteners, or 187 and 75 with a 10% allowance. At 50 psf, each ledger hanger carries 50 × 1.333 × 12 ÷ 2 = 400 lb and each stair-header hanger 200 lb, 44% and 22% of a 900 lb catalogue rating. The ledger's own attachment to the house is a separate check.
Who it is for and when to use it
Ordering hangers and fasteners
Turn a framing plan into a hanger count by size and a fastener order with spares, so the right boxes arrive before framing starts.
Deck ledgers and stair openings
Count hangers along the ledger and around openings, and check the reactions against the hanger you plan to buy. Pair it with the decking board calculator for the deck surface.
Floor framing schedules
List every header in a floor with its joist size and plies, and export the schedule for the drawing set or the supplier.
Checking a substitution
When a site swaps a hanger model, enter the substitute's rating and fastener schedule to see whether every row still works.
Method, formulas & assumptions
Joists per header = entered count, or ceil(header run ÷ spacing) + 1; hangers = joists × hung ends (one or both). Header and joist fasteners = hangers × fasteners per hanger, with the allowance rounded up. Reaction per hanger = (dead + live) × spacing × joist span ÷ 2; utilisation = reaction ÷ the allowable load you enter. Hangers are totalled by generic type, plies and joist size.
Imperial inputs are converted with exact factors (1 ft = 0.3048 m, 1 lb = 0.45359237 kg, 1 US gal = 3.785411784 L) before the calculation runs in SI, then results are converted back.
Common mistakes to avoid
- Forgetting the first joist. A run divided by the spacing gives the number of gaps; add one for the joists.
- Using a rating for a different fastener. Catalogue loads assume the listed nails or screws in every hole.
- Ignoring doubled members. Trimmers and joists that carry a header take far more than the spacing-based reaction.
- Using standard galvanized hangers on treated lumber. Match the corrosion protection to the treatment and exposure.
- Hanging joists from a ledger without checking the ledger. The ledger's bolts or screws into the house are a separate, often critical, connection.
Scope & limits
Hanger ratings and fastener schedules are the values you enter from the manufacturer's catalogue for the exact model, fasteners, species and load duration; names are generic. Doubled members carrying point loads, skewed or sloped hangers, uplift, the header or ledger's own capacity and corrosion protection need separate checks.
Frequently asked questions
How do I calculate how many joist hangers I need?
Divide the header run by the joist spacing, round up and add one. A 16 ft ledger at 16 in centres needs 13 hangers; joists hung at both ends need two each.
How much load does a joist hanger carry?
Each hanger carries the joist's end reaction: (dead + live load) × spacing × span ÷ 2. At 50 psf, 16 in centres and a 12 ft span, that is 400 lb.
How many nails go in a joist hanger?
As many as the catalogue specifies for that model, in every hole. The calculator multiplies the header and joist fasteners per hanger that you enter and adds an allowance for the order.
Can I use screws in joist hangers?
Only screws the hanger manufacturer lists for that hanger. General-purpose wood, deck or drywall screws are not rated for hanger loads.
Do I need joist hangers on a deck?
Joists that frame into a ledger or a flush beam need hangers or another rated connection. Joists that sit on top of a beam bear on it and are usually fixed with ties instead.
Does the calculator work in metric?
Yes. Switch to Metric for metres, millimetres, kilopascals and kilonewtons. A 4.8 m ledger at 400 mm centres takes 13 hangers.
Does it choose a hanger model?
No. Names are generic, such as a face-mount hanger for a 2x10. Choose the model, its rating and fasteners from the manufacturer's catalogue.
Do I need an account to download the result?
No. All calculations, local file processing and exports on this page are free, without an account.
Where are my inputs stored?
The tool keeps inputs in this browser tab. It does not upload them or create a cloud copy. Save or download anything you want to keep before leaving the page. Standard site analytics may operate independently of the tool.
Can I work in metric instead of imperial?
Yes. Use the Imperial / Metric switch above the inputs. Imperial (feet, inches, pounds, gallons) is the default; switching converts every dimensional field and result, and your choice is remembered across the free tools in this browser.
Further reading
- Deck, pergola and shade structure template
- Building permit process explained
- All framing & structure tools
- All free architecture & construction tools
- Harth resource library
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