Translate a supplied opening into overlay or inset leaf dimensions.
Where does the centre gap belong when two equal doors share one opening?
Use the matching calculator
Use this decision sequence
- Measure the clear opening, rather than an existing door face.
- Enter the chosen outside overlay as positive, or inset reveal as negative.
- Deduct the selected centre gap once across a two-leaf pair.
- Check each resulting leaf against the hardware and tolerances already specified in your plan.
Keep the quantities distinct
| Quantity or assumption | How to use it |
|---|---|
| Outside overlays | Extend the combined face at the outer sides. |
| Centre gap | Separates leaves and is deducted only between them. |
| Single leaf | Does not contain an internal centre gap. |
Worked comparison
A 1 m opening with 20 mm overlay on each outside side has 1.04 m total face width before the centre gap. Two equal leaves separated by 4 mm are each (1.04−0.004)/2 = 0.518 m wide. For an 0.8 m opening and 20 mm top and bottom overlays, each leaf is 0.84 m high.
Check before using the estimate
The calculator translates your specified overlays. It does not choose hinges, tolerances, door swing clearances or a mounting method. The example values are illustrative arithmetic inputs. Replace them with your measured plan, selected product information and actual quote where relevant.
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.