Façade Proportion Calculator
The proportion of a façade or an opening — width to height — against the ratios architects have used for centuries, and the dimension that would bring it to the nearest one.
Proportion systems are ratios: the golden section at 1.
How the façade proportion calculator works
Proportion systems are ratios: the golden section at 1.618, the root-two rectangle at 1.414, the double square at 2, the 3:2 and 4:3 of classical orders. A façade sits near one of them or between two.
None is a rule. What the comparison gives you is a vocabulary — knowing your elevation is a slightly stretched root-two tells you what a 300 mm change would do to it.
Formula: ratio = longer side / shorter side; compare against named ratios
Worked examples
| Inputs | Proportion (long : short) | Note |
|---|---|---|
| 14.5 by 9 m | 1.6111 | close to the golden section |
| A square | 1 | exactly 1 |
| A tall opening | 2 | a double square, portrait |
FAQFrequently asked questions
What is the golden section?
A ratio of about 1.618, where the whole is to the larger part as the larger part is to the smaller. It appears in classical and Renaissance façades and is still used as a check.
Do proportions actually matter?
Not as rules, but a façade that sits near a simple ratio tends to read as resolved, and one that sits between two tends to read as slightly wrong without anyone knowing why.
What is a root-two rectangle?
One whose sides are in the ratio 1 : 1.414 — the proportion of an A-series sheet, and of many Gothic plans.
Which proportion should I use?
The one that suits the building and the site. The value of this page is knowing which one you are near and how far you are from it.
Does this work for windows and doors?
Yes — openings are where proportion is most noticeable. A door at 1:2.3 and one at 1:2 read very differently in the same wall.
Where these figures come from
- Sabine (1922) — Collected Papers on Acoustics — the reverberation-time equation
- CIBSE Guide A — Environmental design — daylight, comfort and ventilation criteria
- Neufert — Architects' Data — the standard reference for space and dimension
- International Code Council — International Building Code — occupant load and egress factors
- International Code Council — publisher of the model codes most US jurisdictions adopt
Last checked: September 2026. Formulas are the standard building-science and code relationships; default thresholds are common international values and should be replaced with the ones in your code.