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How to Determine the Length of a Window Balance from Sash Height

How to Determine the Length of a Window Balance from Sash Height

Normally, the easiest way to determine the length of a replacement window balance is to measure the old balance. But if the original balance is missing, you may still be able to estimate the correct length using the window sash.

The method depends on the type of balance your window uses. Spiral balances and block and tackle balances are measured differently when using sash height as a reference, so it is important to identify the balance type before choosing a replacement.

Before You Start

You will need a tape measure and access to the window sash. If the original balance is still available, use that as your main reference whenever possible.

Sash-based measuring can be helpful when the old balance is missing, but replacement balance length may still vary by window design, balance style, attachment type, and manufacturer. Always compare available product details before ordering.

Spiral Window Balances

Measure the Full Sash Height

To estimate the length of a spiral window balance without the old balance in hand, raise the sash so the full sash is visible.

Measure the entire sash from top to bottom. This full sash height can help you determine the approximate spiral balance length needed for the window.

Tip: For spiral balances, measure the full sash height, not just the visible glass.

Block and Tackle Window Balances

Measure the Visible Glass Height

For block and tackle window balances, the process is different.

Instead of measuring the entire sash, measure the height of the visible glass only. Do not include the top or bottom sash rails in your measurement.

Tip: For block and tackle balances, measure only the visible glass height. Do not include the sash frame or rails.

Important Reminders

Measuring from sash height is a helpful starting point, especially when the original balance is missing. However, balance length is not the only detail that matters.

Before ordering a replacement, also check:

  • Balance type
  • Balance length
  • Channel width or tube diameter
  • Top and bottom attachments
  • Stamp numbers or markings, if available
  • Sash weight, when needed

Video Guide

Watch the video below to learn more about determining window balance length when the original balance is not available.

Conclusion

If the original balance is missing, sash height can help you estimate the replacement balance length. For spiral balances, measure the full sash height. For block and tackle balances, measure the visible glass height only.

Still need help identifying the correct replacement balance? The WHD team can help you compare measurements, balance style, and hardware details.

Contact the WHD Team

Updated on 20 Jul 2026