How to Single Dose with a Hopper Grinder
Most hopper grinders can be adapted for single dosing with a few simple techniques. You'll never get zero retention, but you can minimize it enough for excellent daily espresso.
⚡ Quick Answer
To single dose a hopper grinder: weigh your beans, use RDT (Ross Droplet Technique — spritz with 1–2 drops of water before grinding), add a bellows attachment to push retained grounds through, and accept that the first gram out may be stale residue from the previous session. Purge 1–2g before your real shot if freshness is critical. Grinders with low retention (under 0.5g) single dose well; high-retention grinders (1g+) waste more coffee.
🎯 Key Takeaway: RDT + bellows handles most hopper grinder single-dosing problems. For truly zero-retention, look at purpose-built single-dose grinders like the Niche Zero.
⚙️ The Core Problem with Hopper Grinders
Hopper grinders are designed to keep beans loaded and grind on demand. This means the grinding path—from hopper throat to exit chute—always has some coffee left inside (retention). When you grind a fresh dose, some of last session's grounds get pushed out first.
Typical Retention by Grinder Type
- • Low retention (under 0.3g): Niche Zero, Lagom P64, most purpose-built single-dose grinders
- • Medium retention (0.3–0.8g): Baratza Sette 270, Eureka Mignon Specialità
- • High retention (0.8–2g+): Baratza Encore, Rancilio Rocky, many budget grinders
✅ Techniques to Single Dose Effectively
1. Ross Droplet Technique (RDT)
Spritz your beans with 1–3 drops of water (use a small spray bottle) before dropping them in the hopper. This reduces static significantly, meaning grounds exit the chute rather than clinging to the sides. RDT won't reduce retention quantity but dramatically reduces grounds stuck inside the grinder.
How much water: Just enough to slightly dampen the surface—beans shouldn't feel wet. About 0.1–0.3ml for an 18g dose.
2. Bellows Attachment
A bellows (rubber squeeze bulb) attaches to the hopper throat and blows retained grounds through when you squeeze it after grinding. This actively purges the chute path. Bellows are inexpensive ($10–20) and work particularly well with grinders that have longer exit paths like the Baratza Encore. Several grinder companies now sell purpose-made bellows accessories.
3. Purge Dose
Before grinding your real shot, grind 1–2g of beans and discard them. This pushes out any retained stale grounds from the previous session, so your actual shot uses only fresh grounds. Wasteful, but reliable for quality-focused brewers.
4. Weigh In + Weigh Out
Weigh your beans before grinding, then weigh the ground output. The difference is your retention. Once you know your grinder's consistent retention (e.g., 0.4g), you can compensate by grinding 0.4g extra each time. This works well once your grinder has a stable break-in period.
When to Consider a True Single-Dose Grinder
If you regularly drink multiple different coffees, care deeply about zero cross-contamination, or your hopper grinder has retention above 1g, a purpose-built single-dose grinder is worth considering. The best low-retention espresso grinders are designed from the ground up for this workflow. See also our guide to espresso grinders under $500 which includes several single-dose options.