Inputs
Example Scenarios
Enter inputs to see a live summary here.
| Door | Existing gap | Old cover | Pad | Pile | Transition | Target | Worst clearance | Trim required | Status |
|---|---|---|---|---|---|---|---|---|---|
| Bedroom 1 | 22 mm | 0 mm | 8 mm | 9 mm | 10 mm | 18 mm | ? | ? | ? |
| Bedroom 2 | 18 mm | 3 mm | 10 mm | 11 mm | 12 mm | 18 mm | ? | ? | ? |
| Closet | 16 mm | 0 mm | 6 mm | 7 mm | 8 mm | 14 mm | ? | ? | ? |
| Hall | 20 mm | 0 mm | 8 mm | 10 mm | 0 mm | 14 mm | ? | ? | ? |
| Office | 12 mm | 0 mm | 12 mm | 12 mm | 15 mm | 18 mm | ? | ? | ? |
| Guest | 25 mm | 5 mm | 8 mm | 10 mm | 14 mm | 18 mm | ? | ? | ? |
Results
Worst-case clearance
—
Swing area vs threshold are both checked; the lower clearance is shown.
Trim required to meet target
—
If zero, your current setup already meets or exceeds the target clearance.
Status
—
PASS means worst-case clearance ≥ target. FAIL means less than target.
Enter your values and click Calculate to see tailored guidance here.
Formula used
Let:
- G = existing gap under door
- R = height removed (old covering)
- C = carpet stack at swing area = pad + pile
- T = transition raise at threshold
- Q = target clearance
Clearance at swing area: G - (C - R)
Clearance at threshold: G - (T - R)
Worst-case clearance: W = min( G - (C - R), G - (T - R) )
Trim required to meet target: U = max( 0, Q - W )
All inputs are normalized to millimeters internally; results are rendered in your selected units.
How to use
- Select units and choose a target clearance preset or set your own.
- Measure the current gap under each door and enter it in the form.
- Enter pad thickness, carpet pile height, and any transition raise at thresholds.
- If you are removing an existing covering, enter its height so the calculator credits that removal.
- Click Calculate to see worst-case clearance, required trim, and guidance.
- Use the CSV and PDF buttons to export the summary and example table.
Safety note: Do not over-trim. Avoid weakening doors by exceeding your safe maximum undercut or manufacturer allowances.
FAQs
It varies by pile and pad. Common practice is 14–18 mm for carpeted floors. Use 18 mm for plush carpet over pad or consult manufacturer guidance, then adjust as needed.
Check both. The door may sweep over carpet inside the room and cross a threshold profile. We evaluate the lower of the two clearances to flag the true worst case.
Enter its height in Existing floor covering to remove. The model subtracts that height from the new build-up so you do not overestimate trimming.
It depends on the door construction. Hollow-core slabs can tolerate less trimming than solid. Use the Safe maximum undercut as a guardrail and verify manufacturer recommendations.
The engine computes in millimeters for precision and converts to your selected units. We also display helpful twin units so installers and clients can compare quickly.