Cable Railing Calculator
Cable railing has to stop a 4 in sphere even when the cables flex, so the runs are set about 3 in apart and the posts no more than 4–5 ft apart. This works out how many cables your guard height needs, how much cable to order, how many end fittings and tensioners, and how many end, corner and intermediate posts — plus a planning cost for the kit or an installed system.
What you'll need
As an Amazon Associate I earn from qualifying purchases.
Muzata 16-20ft Modular Cable Railing Kit for Deck Surface Mount 36in RW17
$339.99
Check price on Amazon
CELYND Stainless Steel Cable for Railing - 500FT 1/8" T316 Wire Rope Cable
Save 15%
$59.24List Price:: $69.69
Egadis 4 Pack 36 in x 6 ft Modular Aluminum Porch and Deck Railing Kit
$619.99
Check price on Amazon
DEWALT 20V MAX Cordless Drill and Impact Driver, Power Tool Combo Kit , Includes 2 Batteries, Charger and Bag (DCK240C2)
Save 25%
$179.00List Price:: $239.00
Prices and savings as of Sep 30, 2026, 4:35 AM UTC. Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.
How a cable railing is laid out
A cable railing is a set of horizontal stainless cables stretched between a top rail and the deck, anchored at end and corner posts and passing through intermediate posts. Because a cable flexes when you push it, the gaps have to be smaller than the 4 in sphere rule allows for rigid balusters — about 3 in on centre is standard — and the posts have to be close enough to limit the flex, usually 4 ft and at most 5 ft.
Cables per guard height
| Guard height | Clear height for cables | Cables at ~3 in |
|---|---|---|
| 36 in | about 32½ in | 10 |
| 42 in | about 38½ in | 12 |
The clear height allows for the top rail and a small gap at the deck. The calculator spaces the cables evenly inside it and shows the actual gap, which should stay under 3 in.
Fittings and posts
Cables are tensioned one straight section at a time. Every cable in every section needs two terminations — a tensioner at one end and a fixed or swaged fitting at the other — so a three-sided deck with 10 cables needs 60 fittings. End and corner posts take the combined pull of every cable, which adds up to thousands of pounds, so they must be rated for cable (most metal cable posts are) or, in wood, be 6×6 or doubled and well braced. Intermediate posts only guide the cables and stop them flexing.
Ordering cable
Order by the run: each cable is the length of the railing plus a little at every termination for the fittings, and 10% for waste. Buying one continuous reel is cheaper than pre-cut lengths if you have a swaging tool or use push-lock fittings. Use 316 stainless near salt water or pools; 304 rusts faster there.
Is cable railing right for your deck?
- Views. It is the least visible guard after glass, which is why people choose it.
- Children. Horizontal infill can be climbed; some jurisdictions restrict it, and some parents avoid it.
- Maintenance. Cables need re-tensioning after the first season and occasionally after that.
- Cost. Two to four times a basic wood railing.
Compare it with other styles in the deck railing cost calculator and our best deck railing guide. Height and opening rules are in the deck railing height code guide; for picket railings, count spindles with the deck baluster calculator.
Get the Smart Decking Calculator app for Android
Estimate decks on the go, save projects, and share them with contractors.
Building something else? Try our sister calculators
Smart Fencing Calculator
Estimate fence cost by material and linear footage.
Smart Roofing Calculator
Free roof replacement cost estimates by material.
Smart Drywall Calculator
Android app — drywall sheets, mud, and tape estimates.
Smart Fencing Calculator
Android app — fence cost estimates on the go.
Frequently asked questions
- How many cables do I need for a deck railing?
- With cables about 3 in apart, a 36 in guard needs 10 cables and a 42 in guard 12. The gap stays under 3 in so that a 4 in sphere still cannot pass when a cable is pushed sideways.
- How far apart should cable railing posts be?
- Most systems want posts no more than 4 ft apart, some allow 5 ft. Wider spacing lets the cables deflect too far under a push and fail the 4 in sphere test.
- How much does cable railing cost?
- For a typical 40 ft, three-section deck railing this calculator's planning range is roughly $65–$140 per linear foot for a kit with metal posts and $100–$230 per linear foot installed. Wood posts bring the kit price down; custom stainless pushes it up. It is two to four times the cost of a basic wood railing.
- Is cable railing up to code?
- It is accepted in most US jurisdictions when it passes the 4 in sphere test under load and the posts resist a 200 lb outward force. Some areas restrict horizontal infill because children can climb it, so check with your building department first.
