China vs US Building Material Sizes & Standards

China and US building-material sizes are convertible, but they are not automatically interchangeable. One inch equals exactly 25.4 mm, yet a 900 × 2100 mm door is not a 36 × 84 in door, and a 600 × 1200 mm tile is not a true 24 × 48 in tile. Converting the numbers is only the first step. A safe purchase must also define what the dimension measures, the allowed tolerance, the installation interface and the required performance evidence.

There is no single China-to-US chart that can replace the project drawings, specifications, adopted local code and design-team decisions. US jurisdictions may adopt model codes with local amendments, while product standards cover different aspects of performance. The project’s architect, engineer, code consultant and authority having jurisdiction should identify what applies. This guide is a procurement tool, not a code-compliance determination.

Capable Chinese manufacturers can produce project-specific inch or metric dimensions. What matters is whether the approved drawings, samples, tests and production controls describe the same product.

Table of Contents

1. Why a direct China-to-US size chart is not enough
2. Metric and imperial conversion tables
3. China vs US door sizes and specifications
4. China vs US window sizes and performance
5. China vs US cabinet dimensions
6. China vs US tile sizes and test data
7. RFQ and BOQ fields you should include
8. A conversion-controlled sourcing workflow
9. Common mistakes
10. Frequently asked questions
11. Source building materials from China with fewer dimensional risks

Why a Direct China-to-US Size Chart Is Not Enough

Chinese factories commonly prepare production drawings in millimeters, while US architectural documents commonly use feet, inches and fractions. The harder differences are hidden behind the numbers.

Use one production-control dimension and show the other unit as a reference: “Door leaf: 914.4 × 2133.6 mm, controlling; reference only: 36 × 84 in.” Do not round it to 900 × 2100 mm without an approved revision.

For an end-to-end overview of supplier selection, samples, inspections and logistics, see How to Source Building Materials from China for Construction Projects.

Metric and Imperial Conversion Tables

The exact length relationship is:

Millimeters = inches × 25.4 Inches = millimeters ÷ 25.4

NIST confirms that one inch is exactly 25.4 millimeters. Keep enough decimal places during coordination, then apply the specified manufacturing tolerance.

Common Fractional-Inch Conversions

Near-Matches That Are Not Equal

These differences are not suggested tolerances. They show why substituting the nearest familiar module can cause cumulative alignment problems.

China vs US Door Sizes and Specifications

A factory may write “door size 900 × 2100 mm,” but that phrase is incomplete. It might mean the leaf, the outside of the frame or the required wall opening. A US schedule may list a nominal leaf size while the rough opening appears only in the manufacturer’s installation details.

For example, a 900 × 2100 mm leaf converts to approximately 35.43 × 82.68 in. It is not a 36 × 84 in leaf. If the project requires 36 × 84 in, the controlling metric size is 914.4 × 2133.6 mm before any approved manufacturing tolerance.

Door Dimensions You Must Confirm

• Opening mark and exact building location
• Finished wall opening or rough opening, width × height
• Frame outside dimension and frame throat/jamb depth
• Door leaf actual width × height × thickness
• Clear opening required after the leaf and hardware are installed
• Head, jamb, threshold, undercut and floor-finish relationships
• Single or pair configuration; active/inactive leaf and astragal details
• Handing, hinge side and inward/outward swing, shown on a plan
• Sidelight, transom, glazing and louver dimensions
• Hinge, lock, closer, panic/fire-exit hardware and access-control preparation
• Wall anchors, reinforcement, sealant joint and perimeter interface

Door Performance and Evidence You Must Confirm

• Interior or exterior use, exposure and expected duty level
• Door and frame material, core/construction, face thickness and finish system
• Structural, air and water performance values when required for the exterior assembly
• Thermal values for an eligible exterior door product when the project specifies NFRC-rated performance
• Fire-protection rating, test/listing basis, label and compatible frame, glazing and hardware when a rated opening is required
• Acoustic, forced-entry, impact, corrosion or accessibility criteria only where the project requires them
• Standard designation and edition, test pressure/acceptance criteria, laboratory, report number and tested specimen size

ANSI/SDI A250.8 covers standard steel-door and frame construction and performance classifications, while requiring users to coordinate applicable codes. For rated openings, do not approve a “fireproof door” claim or leaf certificate alone. UL explains that the frame, glazing, hardware and accessories may form the rated assembly.

ASTM E283/E283M, E330/E330M and E331 address air leakage, structural performance and water penetration. A test-method number alone does not set the required pressure or acceptance value.

For a door-specific submittal checklist, read the Villa Entry Door Specification Buyer Guide.

China vs US Window Sizes and Performance

Window risk begins when “size” is left undefined. Your schedule should distinguish the wall opening, unit/frame size, daylight opening, operable clear opening and glass size. Mulled combinations also need the overall assembly dimension and individual unit dimensions.

Window Dimensions You Must Confirm

• Window mark, elevation, floor and room location
• Operating type: fixed, casement, awning, sliding, hung or another approved configuration
• Rough opening and finished opening
• Overall frame/unit width × height × depth
• Daylight opening and required operable clear opening
• Mullion/transom positions, coupling details and combination size
• Sill, head, jamb, receptor/subframe, flashing and drainage interfaces
• Glass make-up, pane thicknesses, air/gas spaces, coating surface and safety-glazing locations
• Frame material, profile series, thermal break, finish and color
• Hardware, screens, restrictors/limiters and insect-screen mesh where required
• Anchor type, spacing responsibility, perimeter sealant and installation tolerances

Window Performance and Evidence You Must Confirm

• Project design pressure and any required performance class/grade
• Air leakage, water penetration and structural test requirements
• U-factor, solar heat gain coefficient (SHGC), visible transmittance (VT), air leakage and condensation rating/index where specified
• Acoustic, impact, security or special environmental requirements where applicable
• Exact test/certification standard edition and product designation
• Certified product directory entry, label or project-specific certificate where required
• Tested unit size, operator type, frame, reinforcement, mullions, glass and hardware matching the proposed configuration

The North American Fenestration Standard, AAMA/WDMA/CSA 101/I.S.2/A440 (NAFS), is a material-neutral performance standard for covered fenestration. FGIA distinguishes Performance Grade from design pressure because PG includes other applicable requirements. A new NAFS edition does not automatically govern every project; specify the required edition.

NFRC ratings address energy characteristics such as U-factor, SHGC and VT; they do not replace NAFS structural, air and water requirements. A glass-center value is not a certified whole-product rating.

See the China Window Buyer Guide for deeper coverage of profiles, glass, hardware, samples and inspection.

China vs US Cabinet Dimensions

Cabinet dimensions form a coordinated system. US drawings may use nominal inch modules, while a Chinese factory works in millimeters. A 24 in depth is 609.6 mm—not 600 mm—and the difference can affect countertops, appliances and services.

Do not assume a familiar “standard cabinet size” controls a custom project. Coordinate base height with the countertop, and depth with fronts, handles, services and appliances. Framed, frameless, inset and overlay construction create different usable openings.

Cabinet Dimensions You Must Confirm

• Cabinet mark, room, elevation and drawing revision
• Framed or frameless construction; inset, partial-overlay or full-overlay fronts
• Overall width × height × depth for every unit
• Face-frame, door, drawer and clear internal opening dimensions
• Toe-kick height/depth, finished end panels, fillers, scribes, light rails and crown
• Actual side, bottom, shelf, back and door-panel thicknesses
• Countertop, substrate, backsplash, overhang, sink and faucet interfaces
• Appliance model numbers, manufacturer cutouts, ventilation and door-swing clearances
• Plumbing, electrical, gas and data cutouts or service voids
• Hinge angle, drawer extension, adjacent-wall and corner clearances
• Installation datum, wall condition, anchorage, levelling and site-measure responsibility

Cabinet Performance and Evidence You Must Confirm

• Substrate identity and grade, veneer/laminate/coating, edge-banding system and exposed-edge finish
• Moisture, heat, stain, chemical and scratch performance appropriate to the location
• Hardware manufacturer/model, load rating and cycle evidence where specified
• Shelf, drawer, hanging and wall-mount performance requirements
• Approved finish sample, color tolerance, sheen and grain matching
• Packaging method for assembled or flat-pack delivery and site assembly instructions
• Composite-wood emissions documentation and labeling when applicable to the US import

ANSI/KCMA A161.1 covers kitchen and vanity cabinet performance and construction, including structure, door/drawer operation and finishes. It does not prescribe project appearance or dimensions. State whether certification is required and which product line is covered.

For cabinets containing covered hardwood plywood, MDF or particleboard, the US importer should confirm current TSCA Title VI responsibilities. EPA guidance covers composite wood and finished goods containing it; an informal “E0” claim is not equivalent to US documentation.

China vs US Tile Sizes and Test Data

Tile names are prone to false equivalence. A 600 × 1200 mm tile measures about 23.62 × 47.24 in; a true 24 × 48 in product is 609.6 × 1219.2 mm. They create different grids, cuts and quantities.

Tile has a nominal size, measured facial/work size, thickness and manufacturing variation. Its installed module includes the grout joint, so approve the product with the layout and joint plan.

Tile Dimensions You Must Confirm

• SKU, series, color, finish and intended wall/floor/interior/exterior use
• Nominal size and declared actual/work size, clearly labelled
• Thickness and allowable dimensional/warpage variation
• Rectified or non-rectified edges and edge profile
• Approved grout-joint width and installed module
• Layout datum, orientation, pattern, vein direction and pattern repeat
• Shade, caliber and production-lot controls
• Pieces per carton, net coverage, carton/pallet weight and pallet dimensions
• Quantity by area, cutting waste, attic stock/spares and replacement-lot strategy
• Bullnose, cove, step, corner, mosaic and other trim units
• Mosaic sheet size, chip size, mesh/paper mounting and joint consistency

Tile Performance and Evidence You Must Confirm

• Product classification and relevant criteria under the specified edition of ANSI A137.1, where required
• Water absorption tested by the specified method, such as ASTM C373
• Facial dimensions and thickness under ASTM C499 when specified
• Breaking strength under ASTM C648 when relevant
• Freeze-thaw, abrasion, stain and chemical resistance appropriate to the application
• Wet-use classification or friction test data under the specified method, such as ANSI A326.3, where applicable
• Test report product identification, sampling date, lot, laboratory, edition and measured results—not merely “pass”
• Mortar, adhesive, grout, membrane, substrate and installation-method compatibility

ANSI A137.1 is a voluntary ceramic-tile specification. ASTM methods measure individual properties; the architect and tile professional must still define the application and acceptance criteria.

RFQ and BOQ Fields You Should Include

A useful RFQ lets two suppliers quote the same product without guessing. Include these fields in the BOQ or specification schedule.

Project-Level Fields

• Project name, country, state/city and building use
• Drawing/specification issue date and revision register
• Code and standard editions identified by the project design team
• Controlling measurement system and rounding rule
• Incoterm, named port/place, destination and required-on-site dates
• Submittal, sample, mock-up, first-article and inspection requirements
• Approved laboratory, certification, label and document requirements
• Packing, marking, pallet, container-loading and damage-protection rules
• Warranty, spare quantity, replacement parts and defect-correction process

Line-Item Fields

When your drawings and BOQ are ready, use How to Send BOQ and Drawings to a China Sourcing Agent to prepare a cleaner enquiry package.

A Conversion-Controlled Sourcing Workflow

1. Freeze the governing documents. Identify the current architectural drawings, schedules, specifications and local-code assumptions supplied by the design team.
2. Choose one controlling unit. Show dual units for communication, but state which value controls manufacturing and inspection.
3. Require supplier redlines. The factory should mark every conflict, proposed substitution, tolerance and interface assumption before pricing is finalized.
4. Approve coordinated shop drawings. Check openings, interfaces, hardware, glass, appliances, joints and installation—not only the visible product dimensions.
5. Approve physical samples or a first article. Link each signed sample to an item code, finish code and drawing revision.
6. Inspect against the same data. Pre-shipment inspection should use the approved shop drawings, tolerances, samples, test evidence, labels and packing specification.

Common Mistakes

1. Rounding to the Nearest Familiar Module

Changing 914.4 mm to 900 mm or 1219.2 mm to 1200 mm is a design change, not formatting.

2. Writing “Door Size” or “Window Size” Without a Datum

State leaf, frame, rough opening, clear opening or glass size. Add a section detail when words are insufficient.

3. Converting Nominal Size but Ignoring Actual Size

This is common with tile, cabinets and framed openings. Control the manufactured and installed dimensions.

4. Forgetting Joints and Clearances

Sealant joints, grout, fillers, scribes, shims, thresholds, floor finishes and appliance ventilation consume space.

5. Accepting an Unmatched Test Report

Compare the ordered model, dimensions, configuration, material, reinforcement, glass and hardware with the tested specimen.

6. Naming a Standard Without Its Edition or Required Value

“ASTM tested,” “AAMA standard” or “ANSI compliant” is incomplete. Define the edition, property, test condition and acceptance criterion required by the project.

7. Treating Certification as Design Approval

A listing or label can support a submittal, but it does not resolve layout, local amendments, installation or project-specific engineering.

8. Starting Production Before Interface Approval

A correct factory product can still fail on site if the wall, floor, services or adjacent trade differs from the assumption.

Frequently Asked Questions

Is a 900 mm door the same as a 36 in door?

No. A 900 mm dimension equals about 35.43 in, while 36 in equals exactly 914.4 mm. Also confirm whether the number describes the leaf, frame or opening.

Is 600 × 1200 mm tile the same as 24 × 48 in tile?

No. It is close in name but smaller in both directions. The difference affects the grid, cuts and quantity. Specify actual/work size, joint width and layout.

Can Chinese factories manufacture exact US sizes?

Many can manufacture custom sizes, but capability must be confirmed for the specific material, profile, hardware, tooling, tested size range and order quantity. Approve shop drawings and a sample or first article before mass production.

Should the RFQ use inches or millimeters?

Use the project’s primary system and provide a carefully checked reference conversion when it helps communication. State which unit controls. Do not allow both rounded values to act as independent requirements.

Which US standard applies to imported doors and windows?

There is no single answer. The product type, building use, location, adopted code edition, local amendments and project specification determine the framework. NAFS, NFRC, ASTM, ANSI/SDI, UL or other documents may address different properties. The design professional should identify the applicable requirements.

Do I need NAFS and NFRC for the same window?

Possibly, if the project specifies both. They address different performance areas: NAFS covers applicable fenestration performance requirements, while NFRC provides standardized energy ratings. Neither should be substituted for the other.

How much manufacturing tolerance should I allow?

There is no universal tolerance for all four product categories. Use the applicable product standard, manufacturer’s qualified process and project interface requirements. Put the agreed tolerance on the approved shop drawing and inspection checklist.

Is a Chinese domestic test report sufficient for a US project?

Not automatically. First identify the required standard, edition, laboratory/accreditation conditions, product match and acceptance authority. Ask the architect, consultant, client and authority having jurisdiction what evidence they will accept before ordering tests or production.

Source Building Materials from China With Fewer Dimensional Risks

The safest China-to-US purchase is not based on a generic conversion chart. It is based on a controlled chain: project requirement → quotation-ready specification → coordinated shop drawing → approved sample → matching test evidence → inspection → protected delivery.

FBM Sourcing helps US owners, contractors, architects and procurement teams turn BOQs and drawings into factory-ready packages, coordinate samples and shop drawings, consolidate building-material categories and inspect production before shipment.

If you are planning doors, windows, cabinets, tiles or a multi-category package, send your BOQ and drawings to FBM Sourcing for a project-specific sourcing review.

Official References Used for Standards Verification

• NIST: SI Units—Length
• ICC: Code Adoption Resources
• FGIA: North American Fenestration Standard Overview
• FGIA: Fenestration Performance Class Overview
• NFRC: Residential Product Certification and Ratings
• ASTM E283/E283M: Air Leakage of Exterior Fenestration
• ASTM E330/E330M: Structural Performance of Exterior Fenestration
• ASTM E331: Water Penetration of Exterior Fenestration
• Steel Door Institute: ANSI/SDI A250.8
• UL Solutions: Fire-Rated Doors and Related Hardware Application Guide
• KCMA: ANSI/KCMA A161.1 Performance and Construction Standard
• US EPA: Formaldehyde Emission Standards for Composite Wood Products
• TCNA: ANSI A137.1 Specifications for Ceramic Tile
• ASTM C373: Water Absorption of Ceramic Tile
• ASTM C499: Facial Dimensions and Thickness of Ceramic Tile
• ASTM C648: Breaking Strength of Ceramic Tile
• TCNA: ANSI A326.3 Test Method for Measuring Dynamic Coefficient of Friction

Standards and model codes are revised, adopted and amended over time. Confirm the governing edition, project specification and local requirements before procurement.

Related: working with a building material sourcing agent in China · China building materials procurement service