Feet to Meters for Construction and Altitude (ft to m)

Reading a Drawing in Feet When the Rest of the Job Is Metric

Construction is one of the last places where two measurement systems genuinely collide in the same document. An American consultant issues sections dimensioned in feet and inches; the contractor sets out in millimetres; the structural model wants metres; and the drone survey that checks it all reports altitude in feet regardless of where it is flying.

This page covers the one conversion that sits underneath all of that — feet into metres — with the building and altitude figures you are most likely to be checking against.

The international foot is defined as exactly 0.3048 m, so m = feet × 0.3048. A 100 ft elevation is 100 × 0.3048 = 30.48 m, roughly a ten-storey building.

Where It Matters

Construction & Architecture

Sections, levels and setting-out points arrive in feet on US-originated drawings and have to be issued metric on site.

Real Estate

Listings quote ceiling heights and lot frontages in feet, which tells a metric buyer very little until it is translated.

Altitude & Airspace

Aircraft and drone ceilings are stated in feet worldwide, while terrain elevation on the map underneath is in metres.

Taking Dimensions Off a Set of Drawings

Resolve the inches first

US drawings write dimensions as 8'-6". Divide the inches by 12 and add them on, so 8'-6" becomes 8.5 ft and 12'-3" becomes 12.25 ft.

Enter the decimal feet

The metre value builds as you type and carries up to eight decimal places, which is more resolution than any setting-out tolerance will ever ask for.

Round once, at the end

Convert every dimension at full precision and round only when you write it down. Rounding each step to two decimals and then adding them up is how a wall ends up 15 mm short.

Coming back the other way happens whenever you have to reply to the originating office in their units. The swap arrows between the fields reverse the pair, so a metre figure from the site model goes in on top and decimal feet come out below.

metres = feet × 0.3048 • 8'-6" = 8.5 ft × 0.3048 = 2.5908 m. A mental estimate of feet × 0.3 lands within 2%, which is fine for judging a drawing but never for issuing one.

Storey Heights and Flight Levels Side by Side

Two families of numbers dominate this conversion: the small ones that describe a building, and the large round ones that describe airspace. Both are exact conversions, not approximations.

Reference	Feet	Metres
US door height	6'-8" (6.667 ft)	2.032 m
Standard ceiling	8 ft	2.4384 m
Floor-to-floor storey	10 ft	3.048 m
Drone ceiling (US)	400 ft	121.92 m
US transition altitude	18,000 ft	5,486.4 m
Typical jet cruise	35,000 ft	10,668 m

Precision That Survives a CAD Import

Results carry to eight decimal places from the exact 0.3048 factor, so a converted dimension does not drift when it is scaled or arrayed in a model.

Reverse the Pair for a Metric Spec Sheet

One press on the swap arrows lets you answer a metric query in feet, or check an imperial submittal against a metric performance requirement.

Lift a Bare Figure Into a Schedule

The copy button on each field returns digits with no unit attached, so a door or level schedule in a spreadsheet takes it without any cleaning up.

Go Down to Millimetres for Setting Out

Site dimensions are issued in whole millimetres on most metric jobs. Search the unit list for Millimeter and read the same value at that scale.

Everything here runs in the browser. Nothing is uploaded, so project dimensions you check on a phone at the site office stay on the phone.

Construction and Altitude Questions

How many metres is 100 feet?

Exactly 30.48 m. It is a useful anchor because it scales cleanly: 10 ft is 3.048 m, 1,000 ft is 304.8 m, and 10,000 ft is 3,048 m.

What does a dimension written 8'-6" mean?

Eight feet six inches. The apostrophe marks feet and the double prime marks inches. As a decimal it is 8.5 ft, or 2.5908 m. Fractions appear too — 8'-6 1/2" is 8.5417 ft, or 2.6035 m.

Why is altitude given in feet even over metric countries?

Vertical separation between aircraft only works if every crew and controller uses one scale, and feet were already entrenched when international rules were written. A handful of states, notably China and Russia historically, used metres, which forced level conversions at their borders — a known source of risk that pushed the industry further toward a single unit.

Is a US survey foot the same as the foot used here?

Not quite. The survey foot was 1200/3937 m, a hair longer than the international 0.3048 m, and the US formally retired it at the start of 2023. The gap is about 6 mm over 10,000 ft — irrelevant inside a building, but around 0.6 m across a million feet of state plane coordinates, which is why legacy survey data still needs labelling.

Can I treat one metre as three feet on site?

Only for talking, never for building. One metre is 3.28084 ft, so calling it three feet loses about 8.5%. On a 30 m facade that is more than two and a half metres of error.