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Deck & railing estimator

Deck railing post calculator

Follow the railing around its corners and breaks before counting posts. Connect sections that share a physical post, place opening boundaries, and review the equal post stations along each remaining run.

This estimates railing or guard post quantities only. It does not size or lay out deck-support posts, beams, footings, guards, or connections.

Plan my post positions

Interactive estimator

Map railing runs and their shared posts

Measure section lengths along post centrelines. In Advanced layout, reuse a corner endpoint and position openings by boundary-post centres. An opening at a stair access is a break in the level railing, not a stair-post design.

Measurement system

  1. 01 Measure
  2. 02 Calculate
  3. 03 Review

01 / Your inputs

Measurements

Start with one simple section

Measure post centreline to post centreline

Choose a quick layout below. Add shared corners or exact openings only when the project needs them.

Clarify measurement terms
  • Centreline = middle of one post to middle of the next
  • Section = one uninterrupted railing run
View measurement sketchMeasure post centreline to post centrelineChoose a quick layout below. Add shared corners or exact openings only when the project needs them. Centreline = middle of one post to middle of the next. Section = one uninterrupted railing run.SECTION 1Dashed lines mark post centres

Quick layout

1Measure the section layout

Measure guard-section lengths along post centrelines. Add shared corners or stair openings in Advanced layout so their boundary posts are counted once.

Measurement format: 10.5 ft, 8 ft 3 1/2 in, or 96 in

Advanced layout1 section · 0 corners · 0 openings / gates

Join railing sections where one physical post serves both runs, then locate each opening that needs its own boundary support.

Section connections

Section 1

Endpoint roles · 0 corners

Opening or gates

No positioned openings or gates.

2Divide each uninterrupted railing run

Post centre to post centre; supply your selected system limit. Examples: 10.5 ft, 8 ft 3 1/2 in, or 96 in
Recorded post geometry; the spacing layout does not select a structural post size.
Optional local pricingQuantity works without prices
Optional price per item

The calculation runs entirely in this browser.

On this page
  1. 01Calculator
  2. 02Read the layout as physical post positions
  3. 03Check the junctions before counting
  4. 04A shared corner and an interrupted run
  5. 05How uninterrupted runs become stations
  6. 06What changes a post layout?
  7. 07Take the post plan into the railing takeoff

Read the layout as physical post positions

01Follow one section at a time
The drawing identifies the run and its post stations. Each uninterrupted run has its own equal spacing; one perimeter-wide average cannot locate these posts.
02Reconcile the junctions
A shared corner is one physical post. Terminal and opening-boundary posts are fixed conditions; intermediate posts fill the remaining runs. Keep the endpoint connections visible when checking the total.
03Separate installed positions from extras
Extra posts increase the purchase quantity without adding stations to the drawing. Use the installed layout when checking locations, and the purchase list when ordering.

Check the junctions before counting

  • Using this estimator to select structural post size.
  • Counting shared corners twice.
  • Ignoring an opening that creates terminal conditions.

A shared corner and an interrupted run

1. Two sections sharing one corner

Complete inputs

Layout

Layout type
Custom connected sections
Corner endpoints
1
Endpoint roles
start: terminal; corner: corner; end: terminal
First section
3000 mm; start to corner
Second section
3000 mm; corner to end

Post assumptions

Maximum post spacing
1500 mm
Post face width
100 mm
Extra posts
0

Expected result

Terminal posts
2
Corner posts
1
Gate / opening posts
0
Intermediate posts
2
Extra posts
0
Total posts
5

Manual derivation

  1. Each 3000 mm section divides into two 1500 mm spans and contributes one intermediate post.
  2. The shared corner endpoint is counted once: 2 terminals + 1 corner + 2 intermediate = 5.
2. 10 m railing with a 2 m opening

Complete inputs

Layout

Layout type
Straight
Corner endpoints
0
Endpoint roles
endpoint-start: terminal; endpoint-end: terminal
Section 1
10000 mm; endpoint-start to endpoint-end

Openings and gates

Gate 1 - Section 1
2000 mm wide at 4000 mm from section start

Post assumptions

Maximum post spacing
2500 mm
Post face width
100 mm
Extra posts
2

Expected result

Terminal posts
2
Corner posts
0
Gate / opening posts
2
Intermediate posts
2
Extra posts
2
Total posts
8

Manual derivation

  1. The opening leaves two 4000 mm runs; each divides into two spans and needs one intermediate post.
  2. 2 terminals + 2 opening posts + 2 intermediate + 2 spares = 8.

Auditable calculation record

How uninterrupted runs become stations

A post count and station plan cannot establish how a guard is attached or whether its supports are adequate. Use the entered runs only to plan quantities, then check the chosen post system, site conditions, permits, and applicable rules with the responsible installer or qualified professional.

Formula version
2.0.0
Last reconciled
September 13, 2026
Measurement datum
Section lengths and opening offsets follow the entered post-centre geometry.
Rounding
Each run's span count rounds up so its equal spacing does not exceed the selected maximum. Post quantities remain whole items.
Known exclusions
This does not size posts, connections, guards, beams, footings, or structural attachments.
Review the complete methodology

What changes a post layout?

Are shared corner posts counted once?

Yes. Connected sections reuse one corner endpoint, so the shared physical post appears once in the total.

Why does moving an opening change intermediate posts?

Each fenced run is divided separately. Moving an opening changes the two run lengths, so one side can cross a whole-span rounding boundary.

For railing-post layouts, MaterialNest reconciled the span and shared-corner method on September 13, 2026; connection and support decisions remain outside this record. Editorial and correction policy.