How Specialty Coffee Beans Are Graded and Categorized

When you buy specialty coffee, you're often told it's 'single origin' or 'high altitude'—but what do those terms really mean? And why do some beans cost twice as much as others, even when they look the same? The truth lies in how coffee is processed, sorted, and classified before it reaches your bag. These details determine flavor consistency, cup quality, and price.

To understand specialty coffee grades, focus on four key factors: processing method (washed vs. natural), bean shape (flat vs. peaberry), screen size, and growing altitude. Each factor directly impacts flavor, uniformity, and market value. Here’s how pros evaluate them.

1. Processing Method: Washed vs. Natural

Coffee beans are processed in two main ways after harvest, and the method affects both quality and consistency. Washed (or wet) process beans are removed from their fruit using water and machinery, then dried. This method produces cleaner, more uniform flavors and is considered higher quality. Natural (or dry) process beans are dried with the fruit still on, then mechanically hulled. While cheaper, this method often leads to inconsistent quality due to uneven drying and fermentation.

2. Flat Bean vs. Peaberry

A typical coffee cherry contains two flat-sided seeds (flat beans) that sit facing each other. But about 5% of cherries produce a single round seed called a peaberry. Peaberries are not inherently better or worse in taste—they’re just a different shape. Both flat beans and peaberries can produce excellent coffee, but they’re often sorted and sold separately due to their distinct sizes and densities.

3. Coffee Bean Size: Screen Size and Mesh Numbers

Coffee beans are sorted by size using mesh screens with numbered holes. Larger beans typically have more even roasting profiles and are often associated with higher quality. Here’s how beans are categorized by screen size:

• Flat Beans:
  • Mesh 20–19: Extra Large
  • 18: Large
  • 17: Medium-Large
  • 16: Standard
  • 15: Medium
  • 14: Small
  • 13–12: Extra Small
• Peaberries:
  • 13–12: Large
  • 11: Medium-Large
  • 10: Standard
  • 9: Medium
  • 8: Small

4. Altitude: Elevation and Coffee Grade

Coffee is also graded by the altitude where it’s grown. Higher elevations generally produce slower-growing beans with more complex flavors. The grade categories based on altitude (in meters) are:

Generally, higher-altitude beans (1,200m+) are denser, develop more nuanced flavors, and command higher prices due to lower yields and higher farming costs.

Frequently Asked Questions

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

Washed coffee is processed by removing the coffee fruit using water and machinery before drying, resulting in cleaner, more consistent flavors. Natural coffee is dried with the fruit still on the bean, which can create fruity or funky notes but often leads to less consistent quality due to uneven drying.

Are peaberry beans better than flat beans?

Peaberry beans are not inherently better or worse in flavor—they’re simply a mutation where a single round seed forms instead of two flat seeds. They’re often sorted separately and can roast differently, but their quality depends on farm and processing, not shape alone.

How does coffee bean size affect quality?

Larger beans often roast more evenly and are associated with higher quality, especially in specialty grading. Screens (mesh numbers) sort beans by size—higher numbers like 18–20 indicate larger beans, which are typically preferred for consistency.

Does altitude really affect coffee flavor?

Yes. Higher-altitude coffee grows more slowly, developing denser beans with brighter acidity and more complex flavors. Grades like “Special Grade” (1,500m+) are linked to premium characteristics, while lower altitudes (below 610m) yield simpler, softer profiles.

How are coffee beans sorted by size?

Coffee beans are passed through screens with different-sized holes. The mesh number indicates the size—larger numbers (e.g., 18, 19, 20) mean bigger beans. Flat beans and peaberries have separate size charts, with higher numbers indicating larger or more premium beans.

Recommended FrontStreet Beans for Specialty Grading

Explore FrontStreet Coffee’s Ethiopia Huakui for a bright, floral washed Ethiopian lot grown at high altitude, showcasing the qualities of premium elevation. For a classic washed profile, try their Yirgacheffe, known for citrus and stone fruit notes. If you’re curious about peaberries, their Kenya Little Tomato offers a juicy, winey cup with dense bean structure—ideal for seeing how size and processing shape flavor. All are single-origin, freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.