How Many Spindles Do I Need for My Staircase?

One of the most common questions we receive at Forxa is simply: how many spindles do I need? Get this wrong and you'll either have too few — leaving unsightly, non-compliant gaps — or too many, wasting money on stock you can't use. This guide walks you through the calculation clearly and simply, with worked examples for the situations we're asked about most.

Why Getting the Count Right Matters

Ordering the wrong quantity of spindles causes more disruption than it might seem. Order too few and you're either left with a visible gap at the end of a run, or facing a second order — with the real risk that a small batch variation in finish colour means the new spindles don't quite match the first delivery. Order too many and that's simply wasted spend on stock you'll never use, since bespoke and finished metal spindles aren't typically something Forxa can take back once cut or fitted. Getting the number right first time, with a sensible buffer for cutting and accidental damage, is worth the five minutes it takes to calculate properly.

The UK Building Regulation Rule

Before calculating quantity, you need to know the rule. UK Building Regulations (Part K) state that spindles must be spaced so that a 100mm sphere cannot pass through any gap. In practice, this means the gap between spindles should be no more than 99mm — never 100mm or above.

This applies to any staircase where the drop is more than 600mm — which covers the vast majority of domestic staircases.

Step 1 — Measure Your Staircase

You need a few measurements:

1. The angled section — measure along the pitched handrail from the bottom newel post to the top newel post in millimetres. Do not measure the stair treads — measure the handrail itself.
2. Any horizontal section — if you have a level landing or gallery run, measure that handrail length separately.
3. Your spindle's diameter/width — this changes the maximum spacing you're allowed (see below). Check the product page of the design you've chosen.
4. The width of each tread — if your staircase uses one spindle per tread, you'll need to count the number of treads instead.

Step 2 — Calculate the Number of Spindles

There are two common methods depending on your staircase type. Both account for your spindle's actual diameter, because the gap requirement is about the gap between spindles, not the distance between their centres — a thicker spindle allows a slightly wider centre-to-centre spacing for the same 99mm gap.

Method 1 — Length Method (most common)

Use this formula:

For example: a 3,200mm handrail with 12mm spindles at the maximum 99mm gap gives a pitch of 111mm:

Always round up to the nearest whole number and we recommend ordering 5–10% extra to account for any cutting or damage during installation.

Method 2 — Two Spindles Per Tread

Many traditional staircases use two spindles per tread. Simply count the number of treads (steps) and multiply by two:

For example: 13 treads × 2 = 26 spindles

Quick Reference Table

Based on a 12mm spindle at the maximum 99mm gap (pitch of 111mm). If you're using a different spindle width, or want an exact figure for your own measurements, use the Spindle Calculator — it accounts for the width you enter.

Handrail Length	Approx. Spindles Needed	Recommended Order (inc. 10% extra)
1,500mm (1.5m)	13	15
2,000mm (2m)	18	20
2,500mm (2.5m)	22	25
3,000mm (3m)	27	30
3,500mm (3.5m)	31	35
4,000mm (4m)	36	40
4,500mm (4.5m)	40	44
5,000mm (5m)	45	50

Don't Forget the Landing

If your staircase has a landing with a balustrade (a horizontal section of railing), you'll need to calculate that separately using the same length method, then add the totals together. The Spindle Calculator does this for you automatically when you tick "my run also has a horizontal section."

Worked Examples

Example 1 — Straight flight only

A single straight flight with a 2,800mm handrail, no landing, using 12mm spindles at the maximum 99mm gap (111mm pitch): 2800 ÷ 111 = 25.2, round up to 26, minus 1 = 25 spindles. Adding 10% for cutting and damage gives a recommended order of 28.

Example 2 — Flight plus a galleried landing

A staircase with a 3,000mm angled handrail plus a 1,600mm horizontal landing run, both using 14mm spindles at a 99mm gap (113mm pitch). Angled section: 3000 ÷ 113 = 26.5, round up to 27, minus 1 = 26 spindles. Landing section: 1600 ÷ 113 = 14.2, round up to 15, minus 1 = 14 spindles. Total: 40 spindles, recommended order 44.

Example 3 — Curved or winder staircases

Curved and winder staircases don't have a single straight handrail length, so the length method needs to be applied in shorter straight-line sections rather than one measurement — measure each section of the handrail individually (following the actual curve as closely as practical) and calculate spindles for each section separately before adding the totals. If your staircase has any curved sections, we'd always recommend emailing us your measurements at [email protected] so we can double-check the calculation with you.

Working Out Fixing Brackets

Each spindle needs two fixing brackets — one top, one bottom. The type depends on where it sits: spindles on the pitched (angled) part of the stair need an angled bracket to sit the spindle vertically on a sloped surface, while spindles on a level landing or gallery need a standard flat/fixed bracket. Using Example 2 above: 26 angled spindles need 52 angled brackets, and 14 landing spindles need 28 flat brackets — 80 brackets in total. The Spindle Calculator splits this out for you automatically. Browse the full range on our Spindle Shoes & Brackets page.

Common Mistakes When Calculating Spindle Quantity

• Measuring the treads instead of the handrail — the length method needs the handrail run, not the sum of individual tread widths, which will give a different (and incorrect) figure.
• Assuming a flat 100mm pitch regardless of spindle width — this under-orders for thin spindles and can, in rarer cases, leave the actual gap too wide for thicker profiles if not checked properly. Always factor in your specific spindle's width.
• Forgetting the landing entirely — a very common oversight that leads to a second, smaller order (and a real risk of a slight finish-batch mismatch between the two).
• Not ordering any buffer — even careful installers occasionally damage a spindle during cutting or fitting. A 10% buffer avoids a hold-up waiting on a top-up order.

Important — Check Before You Order

To get the best result, we always recommend double-checking your measurements before ordering. A few things to keep in mind:

• Measuring twice before ordering
• Adding at least 10% to your calculated quantity
• Confirming your spindle width — thicker spindles allow a slightly wider centre-to-centre spacing for the same legal gap
• Consulting a joiner if you are unsure

This guide and the Spindle Calculator are intended as a starting point only — every staircase is different, and quantities should always be confirmed on site with a qualified installer before ordering. Forxa cannot accept responsibility for incorrectly ordered quantities based on these figures alone.

If you have questions about your specific staircase, email us at [email protected] and we will do our best to advise before you order.

Frequently Asked Questions

What if my calculation doesn't divide evenly?

Always round up, never down — rounding up guarantees the resulting gap is at or under the legal maximum. Rounding down would leave a gap larger than intended, which may fail the 100mm rule.

Should I order extra spindles beyond the 10% buffer?

For most projects, 10% is a sensible allowance for cutting waste and accidental damage. If your staircase has an unusual shape, multiple angles, or you're not fitting it yourself, ask us for advice on your specific project before ordering.

Can Forxa help me calculate this myself?

Yes — email your handrail length (or tread count), spindle choice and any landing measurements to [email protected] and we'll confirm the quantities with you before you order.