Deduct divider thickness before dividing equal clear openings.
Why are completed compartments narrower than width divided by count?
Use the matching calculator
Use this decision sequence
- Measure the existing clear inside width.
- Use the number of intended compartments, not the divider count.
- Deduct one supplied divider thickness for each internal divider.
- Divide the remaining clear width by compartment count and check the intended contents separately.
Keep the quantities distinct
| Quantity or assumption | How to use it |
|---|---|
| Four compartments | Need three internal dividers. |
| Inside width | Excludes outer walls already. |
| Clear compartment width | Excludes the internal divider material. |
Worked comparison
An illustrative 1 m inside opening divided into four compartments with 0.02 m dividers has 0.06 m of divider material. Clear width is (1−0.06)/4 = 0.235 m. Simply dividing 1/4 gives 0.25 m and overstates each usable opening by 0.015 m. Applying an outer-wall deduction again would understate it instead.
Check before using the estimate
The layout does not select supports, fixings or safe shelf loads.
All dimensions, product properties, prices and specifications in this example are illustrative arithmetic inputs. Use the values from your measured plan, selected product data sheet and supplier quote. This guide does not choose construction specifications or certify safety.
Calculation and scope checked 2026-10-04. Methods and scope.