How Long Should a Top-Bar Hive Be?

Quite often I see discussions pop up regarding one top-bar hive length or another, and which is best. My hives, based on Wyatt Mangum’s design, are three feet in length. I see that a lot of other people advocate Michael Bush’s recommendation of a 4 foot hive.

After much reading to see if there was a “best” length I realized that even hives of the same length may have very different volumes due to the height and widths of their ends. When I did the calculations I found that most of the most commonly recommended hives have pretty similar volumes despite their difference in length.

By my calculations

  • A 3 foot Wyatt Mangum design has 69 liters of volume.
  • A 4 foot Michael Bush design has 72 liters of volume.

So while there is a 25% difference in length, there is only a 3% difference in volume.

A Top-Bar Hive’s Volume Is More Important Than Its Length

I ran the numbers on several other noted top bar beekeepers and found that nearly all of the recommended hive dimensions yielded a volume somewhere between 70 and 80 liters – only a 14% difference between the smallest and largest. Now when I build my hives I keep them in that range. It’s worth noting that a double deep Langstroth is about 85 liters.

I have made two Top-Bar Hive Volume Calculators in a Google Spreadsheet that you can try.

The first tab is a simple volume calculator for one hive.

Image of top-bar-hive-volume-calculator-2Top-bar Hive Volume Calculator - simple

The second tab in the workbook is rather involved but it allows you to do a volume comparison of hives of your dimensions to the recommended dimensions of Mangum, Chandler and Bush.

Image of top-bar-hive-volume-calculator-2Top-bar Hive Volume Calculator - Advanced

Please note that the spreadsheet is “protected” to ensure that the formulas remain intact. When you open it there will be gray diagonal bars over all of the cells that you can not enter data in. They can be distracting. To turn them off go to the menu, click “View” and click the “Protected ranges” checkmark.

As I note on the spreadsheets, all dimensions for Mangum, Chandler and Bush hives are based on my personal interpretation of each author’s guidance for constructing a top bar hive. My interpretation may not be exactly as each author intended so the resultant dimension and volume calculations should be used as a general, relative guide, not as an absolute comparison tool. And that I may have gotten all of this horribly wrong so please use of this information is at your own risk/discretion. 🙂

Let me know if these are of any help to you and if you have any recommendations on how I might improve them.

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