The symbol for feet is the prime mark, represented as the single apostrophe (') or as a shorthand notation such as ft. This measurement unit appears in everyday contexts like shopping for shoes and in professional fields such as architecture and engineering.
Understanding how the symbol for feet is written, marked, and pronounced helps people avoid costly errors in construction, travel, and international trade. The following sections cover notation, usage, and practical details.
| Symbol | Name | Pronunciation | Common Use Cases |
|---|---|---|---|
| ' (prime) | Foot | Foot or feet | Height, room dimensions, carpentry |
| '' (double prime) | Inch | Inch or inches | Detailed measurements, screens, TVs |
| ft | Foot | Foot | Technical drawings, contracts, signage |
| ′ | Prime | Foot | Mathematics, science, surveying |
| ″ | Double prime | Inch | Precision engineering, optics |
Correct Use of the Feet Symbol in Writing
In written English, clarity is essential when expressing measurements. Using the proper symbol for feet prevents confusion with inches and other units.
The preferred format in most documentation is to combine the numeral with the prime mark (5′) or the two-letter abbreviation ft (5 ft). Style guides often recommend using the prime mark for height and the double prime mark for inches.
Typing the Feet Mark on Different Devices
Users often struggle to insert the symbol for feet on keyboards that do not have a dedicated key. Knowing the correct key combinations makes data entry faster and more accurate.
On Windows, holding Alt and typing 039 produces the prime mark. On macOS, pressing Option plus the backtick key followed by the apostrophe key inserts the correct character. Mobile devices usually hide the symbol in the numbers and punctuation layout.
Feet Symbols in Technical and Professional Contexts
Professionals in construction, aviation, and mapping rely on precise notation to communicate dimensions and clearances. Misplaced symbols can lead to measurement errors and safety risks.
Technical drawings typically use the prime and double prime marks, while project specifications and contracts may prefer the full abbreviation ft. Always follow the standards defined by your industry or client.
Regional Differences in Feet Notation
Countries that use the imperial system consistently apply the symbol for feet in everyday signage and product descriptions. In regions where the metric system dominates, the symbol appears mainly in imported specifications and real estate listings.
Travelers and international buyers should verify whether measurements are shown in feet or meters, particularly when comparing room sizes or vehicle dimensions across borders.
Practical Guidance for Using Feet Notation
Applying consistent rules for the symbol for feet improves readability and reduces errors across documents and teams.
- Use the prime mark (′) for feet and double prime (″) for inches in technical drawings.
- Use the abbreviation ft in reports, contracts, and signage where special characters are hard to render.
- Avoid mixing symbols within the same document to maintain clarity.
- Verify regional standards and client preferences before finalizing measurements.
- Check keyboard shortcuts to insert symbols quickly and accurately.
FAQ
Reader questions
What is the correct symbol to represent feet on a blueprint?
The standard symbol is the prime mark (′) for feet and the double prime mark (″) for inches, as used in technical drawings and blueprints.
How do I type the feet symbol on a Mac keyboard?
Press and hold the Option key, press the backtick key, release both, then press the apostrophe key to create the prime mark for feet.
Is it acceptable to use ft instead of the prime symbol in contracts?
Yes, using ft is widely accepted in contracts and formal documents when clarity is required and typographic prime marks are unavailable. In plain text systems, the prime mark is often replaced with a standard apostrophe, which looks similar to a quotation mark but represents feet.