Bathroom Mirror Size Calculator

Calculate a selected mirror-width range and remaining vertical space from measurements and percentages you enter.

Inputs and method

Each width endpoint is vanity width × entered percentage. The selected bottom edge is faucet-top height + entered clearance; remaining space is ceiling height − selected bottom edge.

All empirical factors, rates, percentages, clearances, product yields, and model values shown as inputs are scenario values supplied by you. Their source or measurement basis appears beside the inputs and result. Units remain visible, calculations use unrounded values, and rounding occurs only for display or a whole-package ceiling.

Interpreting the result

This worksheet does not provide width percentages, clearances, fit approval, mounting advice, or code/safety conclusions.

Treat scenario ranges as sensitivity ranges, not confidence intervals. Check the factor’s version, geography, population or product, system boundary, and date before using the result. A finite arithmetic result does not establish code compliance, certification, safety, forecast accuracy, or model validity.

Validation and rounding

Blank required factors, invalid numbers, prohibited negatives, impossible relationships, and unsupported modes do not produce a result. No malformed value silently selects another branch. Continuous outputs use the precision displayed in the result; package quantities round up only after waste is applied.

Worked example

For a 60 in vanity, 70%–90% gives 42.00–54.00 in. A 36 in faucet top plus 4 in clearance places the bottom at 40.00 in and leaves 56.00 in below a 96 in ceiling.

Frequently asked question

Does this select a compliant mirror? No. It only applies entered percentages and clearance to measurements; verify product, mounting, and code requirements.

Sources

• NKBA, “Newly Updated Kitchen & Bath Planning Guidelines” — web edition; page introduction, accessed 2026-07-09. Route-specific boundary: context and terminology only; it does not supply an entered coefficient, uncertainty, recommendation, or approval.
• NKBA, “Kitchen & Bath Planning Guidelines” — current web edition; bathroom-planning overview, accessed 2026-07-09. Route-specific boundary: context and terminology only; it does not supply an entered coefficient, uncertainty, recommendation, or approval.
• International Code Council, “2021 International Residential Code, Part II” — 2021 edition; table of contents and applicable bathroom provisions, accessed 2026-07-09. Route-specific boundary: context and terminology only; it does not supply an entered coefficient, uncertainty, recommendation, or approval.