Washed vs Natural Coffee Beans: Size, Grade & Bean Type Guide

When you buy specialty coffee, terms like ‘washed’, ‘natural’, ‘flat bean’, and ‘peaberry’ show up often—but what do they actually mean for taste, quality, and roast potential? Whether you’re choosing beans for pour-over, espresso, or cold brew, understanding these specifications helps you make better decisions and avoid inconsistent results. This guide breaks down the key physical and processing differences that define coffee bean grades worldwide.

In short: Washed (or wet-processed) beans are cleaned via water and fermentation, producing uniform quality with bright acidity and clarity; natural (dry-processed) beans dry in the sun with fruit still on, often leading to varied flavour and less consistency. Flat beans (the common two-seed form) and peaberries (single round seeds) differ in shape but usually not in taste. Bean size is graded by mesh sieve numbers, and altitude tiers classify quality from 610 to over 1,500 metres.

Washed vs Natural Coffee Processing

Coffee beans are processed in one of two main ways after harvest: washed (also called wet) or natural (also called dry). Washed coffee is processed by removing the coffee cherry’s skin and pulp using water tanks, friction tools, and fermentation. This method strips away the fruit layer before drying, leading to more uniform bean quality with pronounced acidity, clarity, and cleaner flavours. In contrast, natural processing dries the entire coffee cherry in the sun, with the beans still inside the fruit. Later, a hulling machine removes the dried husk. This method is more variable—resulting in inconsistent quality due to uneven drying and fermentation during the extended outdoor phase.

Flat Beans and Peaberries

A typical coffee cherry contains two oval seeds that face each other, forming a flat seam where they touch—these are called flat beans (or flat berries). Occasionally, a cherry produces just one round seed instead of two; this is a peaberry (or caracol). Though the shape differs, peaberries don’t inherently taste different from flat beans. Most coffee is made up of flat beans, but peaberries sometimes appear naturally and are sorted separately during processing.

Coffee Bean Size Grades

Coffee beans are sorted and graded by size using numbered mesh sieves. The higher the mesh number, the smaller the holes—and thus the larger the beans that are retained. For flat beans, grade sizes are: China-standard No.20 (20–19 mesh) for ‘extra large’, 18 (‘large’), 17 (‘medium large’), 16 (‘standard large’), 15 (‘medium’), 14 (‘small’), and 13–12 (‘extra small’). For peaberries, sizes are: 13–12 (‘large’), 11 (‘medium large’), 10 (‘standard’), 9 (‘medium’), and 8 (‘small’).

Altitude-Based Coffee Grades

Beans are also graded by the altitude at which they’re grown, which strongly influences cup quality. Higher-grown beans typically develop more complex flavours due to slower maturation. The standard grade scale includes: Special Grade (1,500+ metres), Upper Grade (1,200–1,500 metres), Medium Grade (1,000–1,200 metres), Special Grade Washed (900–1,000 metres), Upper Grade Washed (760–900 metres), Premium Washed (610–760 metres), and Standard Washed (up to 610 metres).

Why Processing Matters: Washed vs Natural Outcomes

The way coffee is processed doesn’t just impact uniformity—it shapes the final cup profile. Washed beans, with their cleaned, pre-dried seeds, typically highlight the bean’s inherent characteristics: think citrus acidity, floral notes, and a clean, crisp finish. Natural beans retain more fruit sugars during drying, often yielding heavier body, sweeter tones, and fermented or berry-like flavours—but with greater batch-to-batch variability. That’s why washed coffees are favoured for their consistency in specialty brewing methods like pour-over and espresso.

Frequently Asked Questions

What’s the difference between washed and natural coffee processing?

Washed coffee is processed by removing the fruit and pulp using water and fermentation before drying, resulting in cleaner, brighter flavours and more uniform bean quality. Natural coffee dries the whole cherry in the sun with the beans inside, which can create richer, fruitier flavours but often leads to less consistent quality due to variable drying conditions.

Do flat beans and peaberries taste different?

Flat beans (the standard two-seed form) and peaberries (single round seeds) generally taste the same. The difference is purely physical—peaberries occur when a coffee cherry develops one seed instead of two—but most roasters don’t separate them for taste reasons alone.

How are coffee beans graded by size?

Coffee beans are graded by size using mesh sieve numbers. For flat beans, grades range from 20–19 mesh (extra large) down to 13–12 mesh (extra small). For peaberries, sizes include 13–12 mesh (large) down to 8 mesh (small). The higher the mesh number, the smaller the retained bean.

Why does altitude affect coffee grading and quality?

Higher-altitude coffee beans mature more slowly, developing more complex and refined flavours. Grading scales rank beans from Special Grade (1,500+ metres) down to Standard Washed (up to 610 metres), with higher elevations generally indicating better cup quality and higher market value.

Which processing method is better for consistent quality?

Washed processing generally yields more consistent quality because it removes the fruit before drying, reducing variables like mould or uneven fermentation. Natural processing, while sometimes producing unique flavours, is more prone to batch inconsistency due to outdoor drying risks.

Recommended FrontStreet Washed Process Beans

For a clear example of washed coffee quality, try FrontStreet’s Yirgacheffe from the Gedeb Cooperative—known for bright citrus acidity and floral jasmine notes, especially well-suited to pour-over and cold brew. Their Kenya Little Tomato bean features a double-washed process that enhances sweet-tart profiles with notes of tomato, plum, and blackcurrant, ideal for those who enjoy vibrant fruit layers. For a classic washed profile with chocolatey depth, the Jamaica Blue Mountain No.1 offers balanced hazelnut and caramel tones with low bitterness. All are polished examples of how washed processing highlights clarity and origin character. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.