How to calculate spindles for railing

Written by joey campbell | 13/05/2017
How to calculate spindles for railing
Spindles in banister railings add appeal and safety. (marble stairs image by Daria Miroshnikova from

Railings on stairs, balconies or porches in your home help family members to be safe and steady when using stairs or leaning on banisters. Properly spaced for safety, decorative spindles help to create a more stable railing, and add beauty and appeal to the look. To add spindles, you must first determine how many will be needed.

Determine how far apart you want to space the spindles. If you decide you want to space your spindles four inches apart, for example, measure the width of your spindle at its widest point. If the spindles are 2.5 cm (1 inch) wide, the space of the 10 cm (4 inch) gap plus the 2.5 cm (1 inch) width spindle equals a 12.5 cm (5 inch) space.

Measure the banister's lineal distance inside the banister. If you have more than one banister in which spindles are being placed, measure each one separately, always from inside the banister railing.

Total up the measurements. If, for example, you have measured 3.75 m (12 feet and 6 inches) on two different stair or porch railings, convert your measurements to centimetres, which would be 375 cm (150 inches), deduct 10 cm (4 inches) for the initial gap between the newel and the first spindle. Divide the raining number (140 cm) by 12.5cm (5 inches). This calculation allows for 29.20 spindles, so round up for 30 spindles per railing. You will need 60 spindles for both railings.

Tips and warnings

  • If your spindles are wider than one inch, add the extra width to the space needed between each spindle, then divide into the length which you will convert to inches.
  • Check your county building code to get maximum spacing of spindles. Used for safety, spindles should be placed close enough together to prevent small children from falling through or getting their head stuck in the spindles. While 4-inch gaps are common, your county building code may be different.

Things you need

  • tape Measure
  • Calculator
  • Pen and paper
  • Correct width of new spindles

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