When sourcing coffee from Vietnam, buyers who receive supplier quotations or specifications often encounter screen size references such as Screen 16 or Screen 18. Understanding what coffee bean screen size 16 vs 18 means — and what role it plays in a purchase specification — helps buyers ask the right questions and avoid misunderstandings with suppliers. This page explains what screen size indicates, how it is used in specification, and why screen size is one parameter among several that should appear in a well-written purchase specification.
What Coffee Bean Screen Size Means
Screen size is a way of measuring and categorising the size of green coffee beans. Grading screens are metal plates with circular holes of defined sizes, measured in increments of 1/64 of an inch. A Screen 16 has holes of 16/64 inch — approximately 6.35 millimetres in diameter. A Screen 18 has holes of 18/64 inch — approximately 7.14 millimetres. Beans that pass through a Screen 18 but are retained by a Screen 16 are classified as Screen 16 or 16-up (meaning retained on Screen 16).
In practice, a Screen 18 specification typically means that the majority of beans in the lot are retained on an 18/64-inch screen — they are too large to pass through the holes. A Screen 16 specification means beans are retained on a 16/64-inch screen. A lot sold as Screen 16/18 may include beans of mixed sizes within that range. Tolerance allowances for undersized or oversized beans are usually specified in the purchase contract.
For buyers sourcing Vietnamese Robusta, Screen 16 and Screen 18 are the most commonly referenced sizes in commercial export transactions. Screen 18 lots command a higher price in the market, partly reflecting the labour and processing required to sort larger beans consistently and partly reflecting market convention that larger beans have higher visual uniformity.
Does Screen Size Indicate Quality?
Screen size indicates bean size — it does not directly indicate the flavour quality, moisture content, defect level, or overall suitability of the coffee for a buyer’s application. A Screen 18 lot can have high defect levels or improper moisture; a Screen 16 lot can be a clean, well-processed product that meets all other quality parameters the buyer cares about.
The association of larger screen size with higher quality is a market convention, not a technical fact. Buyers should evaluate screen size as one specification element alongside defect count, moisture range, processing method, and any sensory quality requirements relevant to their end use. If screen size uniformity matters for the buyer’s processing operations — for example, if consistent bean size is important for even roasting — then specifying screen size makes technical sense. If it does not make a practical difference to the buyer’s operations, specifying a higher screen size purely for price signalling reasons may not represent good value.
When Screen Size Specification Matters
Screen size specification matters most in the following situations: where the buyer is producing a product for a market that expects visual bean uniformity (for example, high-end whole bean retail); where the buyer’s roasting process benefits from consistent bean size to produce even roast results; or where the buyer is purchasing for a customer who has specified a particular screen size as part of their own product standard.
For buyers purchasing green beans for blending, instant coffee production, or other processing applications where individual bean appearance is not a consumer-facing feature, the practical significance of Screen 16 vs Screen 18 may be lower. In these cases, buyers should consider whether they are paying a premium for a screen size specification that does not add meaningful value to their product or process.
When including screen size in a specification, buyers should also specify the acceptable tolerance for out-of-screen beans. It is rare for any lot to contain 100% on-screen beans — some undersized or oversized beans are typically present. Specifying the maximum acceptable proportion of off-screen beans (for example, a maximum of 5% below Screen 16 in a Screen 16 lot) gives both parties a clear definition of compliance.
Verifying Screen Size Compliance
Verifying that a supplier has supplied the screen size specified in the purchase order can be done through a sample evaluation at the supplier’s facility or through laboratory grading at an accredited facility. A visual assessment of a sample drawn from the lot gives an approximate indication of whether the beans are consistent with the stated screen size. A formal grading analysis using calibrated equipment provides a more precise measurement that can be documented and referenced in case of a dispute.
Vietnam Biz Rep can include a visual screen size observation as part of a quality inspection visit — noting whether the beans in the drawn sample appear consistent with the stated specification. Where precise grading analysis is needed, buyers should arrange laboratory testing in addition to the physical inspection. For a comprehensive quality specification framework, the Vietnam coffee grades explained page covers all the key grading parameters buyers should include in their purchase specification.
Screen Size in the Context of Your Full Specification
Screen size is one element of a complete green coffee purchase specification. Buyers who specify only screen size and leave other parameters open may receive a lot that meets the screen size requirement but has excessive defects, improper moisture, or a different processing method than expected. A well-constructed specification covers all parameters that are material to the buyer’s end-use application.
Vietnam Biz Rep supports buyers in preparing specification documents, coordinating sample evaluation, and verifying that delivered lots match the agreed specification. For buyers at the beginning of the sourcing process, the Vietnam coffee suppliers overview gives context on the supplier landscape. The supplier verification process confirms supplier legitimacy before orders are placed. For buyers who need a local representative throughout the sourcing process, the Vietnam sourcing agent service covers the full engagement. For guidance on moisture and defect parameters alongside screen size, the coffee moisture and defect requirements page is a useful companion reference.
Communicating Screen Size Requirements to Vietnamese Suppliers
When communicating screen size requirements to a Vietnamese supplier, clarity in the purchase specification reduces misunderstanding. State the screen size requirement explicitly — for example, “minimum Screen 16, maximum 5% below screen” — rather than using terms like “large beans” or “premium grade” without definition. Using measurable parameters in writing creates a clear reference point for both the supplier and any subsequent quality inspection.
If a supplier’s standard offering includes a specific screen size, ask them to provide a sample of that lot so you can evaluate whether it meets your visual and quality expectations before placing an order. Screen size can be observed in the sample — beans that are obviously larger or smaller than the stated size indicate an issue with either the supplier’s grading equipment or their grading practices. Including a screen size check as part of your pre-order sample evaluation process reduces the risk of receiving a lot that does not match your specification.
For buyers who need a local representative to handle these communications in Vietnamese, Vietnam Biz Rep can coordinate with suppliers on specification requirements, obtain samples, and observe the lot condition during an on-site visit. The supplier verification process confirms that the supplier has the processing equipment and grading capability consistent with the screen size specification they are offering. The coffee sourcing agent service covers ongoing supplier communication throughout the order cycle.
Frequently Asked Questions
What is the most commonly traded screen size for Vietnamese Robusta?
Screen 16 and Screen 18 are the most commonly referenced sizes in Vietnamese Robusta export transactions. Screen 18 is priced higher in the market and is often associated with premium commercial Robusta. Screen 16 is also widely traded and appropriate for many applications. The right choice depends on the buyer’s specification requirements and what the lot will be used for.
Can the same coffee lot contain beans of different screen sizes?
Yes. Most lots contain a distribution of bean sizes, and the screen size specification defines the minimum acceptable bean size for the majority of the lot. Tolerance allowances for undersized beans are typically included in the specification. A lot sold as Screen 18 will typically contain some percentage of beans that fall below Screen 18, up to the agreed tolerance limit.
Does Arabica coffee also use screen size grading?
Yes. Screen size grading is used for Arabica as well as Robusta, though the common screen sizes and their commercial significance vary by origin and market. For Vietnamese Arabica, buyers should discuss screen size expectations with their supplier based on the specific lot being purchased, as Arabica production in Vietnam is more variable than the mainstream Robusta market.
Should I always specify screen size in my purchase contract?
You should specify screen size if it is meaningful for your application. If consistent bean size is important for your processing or product presentation, specify it clearly. If screen size does not materially affect your product, specifying it may add cost without adding value. Discuss this with your supplier during the RFQ stage — understanding what screen sizes they typically supply, at what price differential, helps you make an informed decision about what to include in your specification.
To discuss screen size specification and quality verification for your coffee sourcing from Vietnam, contact Vietnam Biz Rep with details about your product requirements and intended application.
