Feet and Inches Calculator

Working with Feet and Inches on the Job Site

Fractions matter on the job site. A measurement that is off by 1/16 of an inch might not matter on a rough framing wall, but it absolutely matters when fitting cabinet doors, setting window trim, or tiling a shower niche. Knowing when to work in fractions and when to round to whole inches is a skill that separates fast, accurate tradespeople from the ones who are constantly re-cutting.

Common measurement scenarios where fractional precision is critical:

• Cabinetry and millwork: Door reveals and face frame gaps are typically set to 1/8" or 3/16" for a clean, consistent look
• Tile layout: Centering a tile run across a shower wall requires splitting inches into fractions to balance the end cuts on both sides
• Stair stringers: Total rise divided evenly across all risers often produces fractions that must be marked precisely on the stringer
• Door and window rough openings: Code and manufacturer specs call out fractions - a 32" door goes in a 34-1/2" rough opening

Using a calculator like this one to add and subtract measurements in feet, inches, and fractions prevents the most common field math errors that lead to wasted materials and callbacks.

Converting Between Measurement Units

Imperial and metric conversions are a daily reality when working with imported fixtures, European appliances, or clients who have metric drawings. The key conversions every contractor should know cold:

• 1 foot = 12 inches
• 1 inch = 2.54 centimeters
• 1 foot = 30.48 centimeters
• 1 meter = 39.3701 inches = 3.28084 feet

Decimal feet vs. fractional inches trip up a lot of people. Surveying and some laser levels report in decimal feet - a reading of 12.75 feet means 12 feet 9 inches, not 12 feet and 75/100 of an inch. When your tape measure shows fractions and your level shows decimals, always convert to a common unit before doing math.

The safest approach on a mixed-unit job: convert everything to total inches first, do your math, then convert back to feet-inches-fractions for marking. That is exactly what this calculator does internally.

Tips for Accurate Measurements

Measure twice, cut once is the oldest rule in carpentry for a reason. But there are a few less-obvious practices that separate consistently accurate work from work that is always slightly off.

• Account for kerf: A standard saw blade removes about 1/8" of material per cut. On a single cut this is minor, but if you are ripping multiple pieces from one board, each cut eats into your usable length. Plan your cuts in order and account for kerf in the total material needed.
• Expansion gaps: Hardwood flooring, LVP, and some tile installations require a gap at walls (typically 1/4" to 3/8" for floating floors). Include this in your layout math so the floor does not buckle in summer.
• Grout joints: Tile measurements need to include the grout joint width. A 12x24 tile with a 3/16" joint covers 12-3/16" x 24-3/16" of floor space per tile, not exactly 12x24.
• Hook play on tape measures: The metal hook at the end of your tape is designed to slide a small amount - exactly equal to its own thickness - so it reads the same whether you are hooking over an edge or pushing the hook against a surface. If the hook is bent or worn, your readings will be consistently off by a fraction.

When to use 1/16" vs. 1/8" precision: Use 1/16" for finish carpentry, cabinetry, and any work that will be seen up close. Use 1/8" for tile and flooring layout. For rough framing and concrete form work, 1/4" is generally close enough.