Granite Slab Thickness Guide: 16mm vs 18mm vs 20mm vs 30mm

  • We’ve had buyers reorder an entire granite shipment because they specified 18mm when their fabricator needed 30mm for an exterior cladding job. Thickness isn’t a minor spec — it determines whether a slab can be used for what you actually need it for, how much a container will weigh, and how much you’ll pay in freight. After supplying granite to fabricators and contractors across 40+ countries for 18 years, here’s the thickness breakdown we walk every new buyer through before confirming an order.

    Why Granite Thickness Matters for Your Project

    Granite thickness affects three things: structural application, weight, and cost. A countertop only needs to support its own weight and whatever sits on it, so a thinner slab works fine. Exterior cladding and flooring under foot traffic or vehicle load need thicker stone to resist cracking. Thickness also changes shipping weight — a 30mm slab can weigh nearly double a 16mm slab of the same dimensions, which directly affects how many square metres fit in a 20ft container and what your per-square-metre freight cost works out to. Getting this wrong after the container is loaded is expensive to fix, so it’s worth confirming before you place the order, not after.

    16mm and 18mm Granite — Best Uses

    16mm and 18mm are the lightest standard thicknesses we supply, and they’re the most common choice for kitchen and bathroom countertops, vanity tops, and interior wall cladding where the stone isn’t bearing structural load. They’re also the most cost-efficient to ship, since more square metres fit into a container at the same weight allowance. The trade-off is that 16mm and 18mm slabs need a stronger substrate or backing for large unsupported spans, so most fabricators add a plywood or honeycomb backing for countertop overhangs beyond 30cm.

    20mm Granite — The Most Common Export Thickness

    20mm is the thickness we ship most often, and for good reason — it’s the standard for kitchen countertops in most international markets, strong enough for unsupported overhangs without backing in most cases, and still light enough to keep shipping costs reasonable. If you’re not sure what thickness to specify and your project is a standard residential or commercial countertop, 20mm is almost always the safe default. Varieties like Black Galaxy and Steel Grey granite are stocked in 20mm as standard.

    30mm Granite — When You Need It

    30mm is specified for exterior cladding, heavy-traffic flooring, monument work, and any application where the stone needs to resist impact or structural load without cracking. It costs more to ship per slab due to weight, but for the right application it’s not optional — using a thinner slab where 30mm is needed risks cracking during installation or under load. If your project involves exterior facades or commercial flooring, confirm 30mm availability with your supplier before finalising drawings.

    How Thickness Affects Shipping Weight and Cost

    Granite weighs roughly 2.6 to 2.7 tonnes per cubic metre, so thickness has a direct, calculable effect on how much fits in a 20ft container and what your freight cost per square metre will be. A container that holds, say, 450 square metres of 18mm granite might only hold around 270 square metres of 30mm granite at the same weight limit. If your budget is tight, specifying the thinnest thickness your application allows is the simplest way to reduce per-unit shipping cost.

    Matching Thickness to Application: A Quick Reference

    As a quick reference: 16-18mm for countertops, vanities and interior cladding; 20mm for standard kitchen countertops and general flooring; 30mm for exterior cladding, heavy flooring and monument work. If you’re working across multiple applications in one project, it’s common to order more than one thickness in the same container to meet your 20 MT minimum order. Our full granite range, including Black Galaxy, Absolute Black and Steel Grey, is available across these standard thicknesses — see our Indian granite exporter page for current stock.

    Get a Quote

    Not sure which thickness your project needs? Send us your application and we’ll recommend the right spec — free quote within 24 hours.


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FAQ's

frequently asked questions

Q What natural stones does Nirvan Exports supply?
A Nirvan Exports supplies five categories of natural stone: marble, granite, sandstone, slate, and limestone. Our marble range includes over 20 varieties such as Makrana White, Rainforest Green, Katni Beige, Fantasy Brown, and Spider Green. Our granite range includes Black Galaxy, Absolute Black, Colonial White, and 15+ additional varieties. We also supply Rajasthan sandstone in Buff, Pink, Teak, and Kandla Grey; natural slate tiles and slate veneer sheets; and limestone including Kota Stone, Fossil, Yellow, and Beige varieties.
A Our minimum order quantity (MOQ) for export is typically 20 metric tonnes per stone type, which equates to approximately one 20-foot container. However, we can accommodate smaller trial orders for new buyers — please contact us to discuss your specific requirements. For large projects requiring multiple containers or regular supply contracts, we offer priority processing and volume pricing.
A Nirvan Exports exports natural stone to over 40 countries worldwide. Our primary markets include the United States, United Kingdom, Germany, Australia, Russia, UAE, Saudi Arabia, France, Italy, Canada, New Zealand, and countries across Southeast Asia, the Middle East, and Africa. We are experienced in the import regulations, documentation requirements, and logistics of all our major export markets.
A Lead time from order confirmation to shipment is typically 15 to 25 working days, depending on the stone type, finish, and order volume. Once shipped from Nhava Sheva port (Mumbai), standard transit times are 18 to 25 days to European ports, 21 to 30 days to USA and Canada, and 12 to 18 days to the UAE and Middle East. We provide tracking information for all shipments.
A Yes. All Nirvan Exports orders can be customised to your project specifications. We supply stone in standard slab sizes (typically 240 x 120 cm), standard tile formats (60 x 60 cm, 60 x 30 cm, 30 x 30 cm), or fully bespoke dimensions cut to your requirements. Available finishes include polished, honed, brushed, sandblasted, flamed, leather, and natural split. Please provide your specifications when requesting a quote.
A Yes. We strongly encourage new buyers to request samples before placing a bulk order. Sample pieces (typically 10 x 10 cm or 20 x 20 cm) are available for most stone varieties in our range. Sample charges and shipping costs apply, which are refundable against your first order. To request samples, contact us with the stone variety, finish, and your delivery address.
A All Nirvan Exports shipments use export-grade wooden crates with foam padding, waterproof wrapping, and heavy-duty strapping. Marble slabs are packed back-to-back with foam separators to prevent surface damage in transit. Slate veneer sheets and fragile stone products receive individual protective wrapping. Our packaging complies with international maritime freight standards and is designed to withstand multi-port transshipment.
A Nirvan Exports is a natural stone supplier and exporter — not a stone manufacturer. Natural stone is quarried from the earth, not manufactured. We own and operate quarry partnerships in Udaipur, Rajasthan and work with established quarry owners across India’s major stone regions. We handle the full supply chain from quarry sourcing through to stone processing, quality control, packaging, and international export.
A Nirvan Exports provides a full set of export documentation with every shipment, including: commercial invoice, packing list, bill of lading, certificate of origin, phytosanitary certificate (where required), and quality inspection report. We are experienced with documentation requirements for all our major export markets including the USA, UK, EU countries, Australia, and the Middle East.
A To receive a quotation, contact Nirvan Exports with the following details: stone type and variety, quantity required (in metric tonnes or square metres), finish required, slab or tile format and size, and your delivery port or country. We respond to all enquiries within 48 hours with a detailed price quotation and, where relevant, availability of samples.
What is the standard granite thickness for kitchen countertops?

20mm is the most common thickness for kitchen countertops internationally, offering a good balance of strength and shipping cost. 16mm and 18mm are also used with added backing support.

Yes, 30mm is generally recommended for exterior cladding and heavy-traffic flooring, since it better resists cracking under structural load and weathering compared to thinner slabs.

Thicker granite weighs more per square metre, which reduces how much fits in a container at the same weight limit and increases your per-square-metre freight cost.

Yes, mixing thicknesses and varieties in one container is common and often necessary to reach the standard 20 metric tonne minimum order.

For overhangs beyond about 30cm, yes — most fabricators add plywood or honeycomb backing to 16mm and 18mm slabs to prevent flexing or cracking.