How do I convert imperial to metric for floor plans?

Use the conversion factor 1 inch = 25.4 mm (or 1 foot = 304.8 mm). For floor plans, convert each dimension separately, then recalculate area in square meters. Arch Convert handles length, area, and volume conversions and lets you type calculations directly.

What is the conversion factor from feet to millimeters?

1 foot equals exactly 304.8 millimeters. This is derived from the base conversion of 1 inch = 25.4 mm, multiplied by 12 inches per foot. For architectural work, avoid rounding until your final measurement.

How do architects convert between imperial and metric?

Architects typically convert using the base factors: 1 inch = 25.4 mm for length, 1 sq ft = 0.0929 sq m for area, and 1 cu ft = 0.0283 cu m for volume. In practice, most use a dedicated converter rather than manual math to avoid compounding rounding errors across a drawing set.

Why do Canadian buildings use both imperial and metric?

Canada officially adopted metric in the 1970s, but the construction industry still uses imperial for many materials. Lumber is sold in imperial dimensions (2x4, 2x6), drywall comes in 4x8 foot sheets, and stud spacing is 16 inches on center. Drawings are metric, but the materials going into the building are imperial. This creates a constant need for conversion.

How do I convert square feet to square meters for a room?

Multiply the area in square feet by 0.0929 to get square meters. For example, a 150 sq ft room is about 13.94 sq m. You can also convert each dimension separately (length and width in meters) and multiply them. Arch Convert does this automatically in the Area tab.

How many acres are in a hectare?

One hectare equals about 2.4711 acres. Going the other way, one acre is about 0.4047 hectares. A hectare is defined as exactly 10,000 square metres, while an acre is 43,560 square feet (4,046.86 m²). Arch Convert's Area tab shows hectares and acres alongside square metres and square feet so you can compare all four at once.

How many square meters are in an acre?

One acre is exactly 4,046.8564224 m² (derived from 43,560 sq ft × 0.3048² m/ft). Arch Convert uses this exact value so round-tripping between acres and square metres doesn't drift. For quick reference: 1 acre ≈ 0.4047 ha, 1 ha = 10,000 m² ≈ 2.4711 acres.

How big is a hectare compared to familiar objects?

A hectare is 10,000 square metres — roughly the size of an international rugby pitch or a FIFA-size football (soccer) pitch plus its surrounds. It's about 2.47 acres, or the size of a typical suburban block in many cities. Land registries in the UK, Australia, New Zealand, Canada, and most of Europe list rural parcels in hectares, while North American land is more often listed in acres — hence the need to convert.

Is Arch Convert free to use?

Yes, Arch Convert is completely free with no signup, no paywall, and no usage limits. It was built by FluxCo Technologies for architects and construction professionals who deal with imperial and metric conversions daily.

How many millilitres are in a cup?

A US cup is 236.59 mL. An Imperial (UK) cup is 284.13 mL. The difference matters for baking, where ratios affect rise and texture. Arch Convert shows both Cup (US) and Cup (Imperial) side by side so you can pick the one your recipe assumes.

What is gas mark 4 in Celsius?

Gas mark 4 is 180 °C (350 °F). The UK gas mark scale runs from ¼ (110 °C) to 9 (240 °C) in 14 °C steps. Gas mark 4 is the most common baking temperature — used for cakes, roast chicken, and most recipes that say 'moderate oven'. Arch Convert's Temperature tab shows Celsius, Fahrenheit, and gas mark in sync.

How many grams of flour are in a cup?

A US cup of all-purpose flour weighs about 125 grams (or 120 g if sifted). This is why baking by weight is more reliable than by volume: flour packs differently depending on how it was scooped. Arch Convert lets you pick the ingredient (water, flour, or oil) when converting grams, because the density matters.

How do I convert 350°F to Celsius?

350 °F is 176.67 °C, usually rounded to 180 °C in recipes (which is also gas mark 4). The formula is (°F − 32) × 5/9 = °C. Arch Convert converts instantly and shows the nearest gas mark alongside.

Why are there US and Imperial cups?

US customary and British Imperial measures diverged after the US adopted its own system in 1824. A US cup is 236.59 mL; an Imperial cup is 284.13 mL — about 20% larger. American recipes assume US cups, British recipes assume Imperial or metric. Using the wrong one changes ratios noticeably, especially in baking.

How many teaspoons are in a tablespoon?

In US measures, 1 tablespoon = 3 teaspoons = 0.5 fl oz ≈ 14.79 mL. So 1 fl oz = 2 tablespoons = 6 teaspoons. Arch Convert's Spoons row toggles between Tsp and Tbsp so you can enter whichever the recipe calls for.

How many grams of butter are in a tablespoon?

One US tablespoon of butter is about 13.5 grams (14.79 mL × 0.911 g/mL density). One US cup of butter is roughly 215 grams, and one stick of US butter (½ cup) is about 113 g. Arch Convert's Grams row has a Butter ingredient option that uses this density automatically.

How big is an Australian / metric cup?

The metric cup used in Australia, New Zealand, and modern Canadian recipes is 250 mL — different from both the US cup (236.59 mL) and the British Imperial cup (284.13 mL). For a typical recipe, using a US cup when an Australian cup is called for means you'll be about 6% short on every measurement. Arch Convert shows Cup (US), Cup (Imperial), and Cup (Metric) side by side so you can translate between all three.

How do I enter feet and fractional inches?

In the Feet & Fractional Inches row, type whole feet in the ft field and a fractional inch value in the in field, for example 5 in ft and 3 1/2 in in for 5 feet 3 and a half inches. You can also write just a fraction like 3/8 or a mixed number like 3 3/8. Values round to 64ths and automatically carry over if inches reach 12 (so 11 15/16" + 1/16" becomes 1' 0").

Arch Convert: Imperial to Metric Converter for Architects

Free online unit converter designed for architects and construction professionals. Convert between imperial and metric measurements for length, area, and volume.

Features

Length: feet-inches, feet + fractional inches (e.g. 5' 3 1/2"), decimal inches, fractional inches, meters, millimeters
Area: square feet, square meters, acres, hectares
Volume: cubic feet, cubic meters, cubic inches, cubic millimeters
Cooking capacity: US / Imperial / Metric (250 mL) cups, US and Imperial pints, fluid ounces, millilitres, teaspoons, tablespoons, and grams by ingredient (water, flour, oil, butter). Show or hide any unit via the Units menu.
Cooking temperature: Celsius, Fahrenheit, UK gas mark
Type fractions directly (e.g. 3/8) and math expressions (e.g. 12.5 * 3)
Drag to reorder conversion sections to match your workflow

Common Conversions

1 inch = 25.4 mm
1 foot = 304.8 mm (0.3048 m)
1 square foot = 0.0929 m²
1 cubic foot = 0.0283 m³
1 US tablespoon = 3 teaspoons = 14.79 mL
1 US fluid ounce = 2 tablespoons = 29.57 mL
1 US cup = 236.59 mL; 1 Imperial cup = 284.13 mL; 1 metric cup (Australia/NZ) = 250 mL
1 tablespoon of butter ≈ 13.5 g (density 0.911 g/mL)
Gas mark 4 = 180 °C = 350 °F

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For architects

Trusted by ZGF Architects and Ryder Architecture. See the architect-focused landing at /for-architects/ for feet + fractional inches, square feet to square metres, and acres to hectares — the conversions architectural drawing sets actually require.

Read our Imperial to Metric Conversion Guide

Built by FluxCo Technologies