But we’re here to talk about single serve coffee, and while using it for one cup is a little trickier (you’ll have to measure smaller quantities of water and coffee), the Four delivered the same bold, balanced brew in a 5-ounce cup, it did in a 20 ounce carafe. I found the recommended 9 grams of coffee lacking, but the instructions advise customizing the ratio a bit, and sure enough a few more grams in the filter did the trick. I found I got the tastiest results brewing two cups (10 ounces), as I think the longer siphoning and heating process with more water flowing through the system was key to a more satisfying extraction. Plus, I like a big cup of coffee.
The Ratio Four comes with a hand-blown 20-ounce glass carafe that also has a sealed lid and a silicone padded bottom. But what I appreciated is the ability to brew directly into any container; there is no hidden button or latch that the carafe needs to activate to brew or let water through. I could use a mug or travel tumbler if I wanted to. And, surprisingly, the same goes for the filter basket, with the Ratio website and instruction booklet explaining that they’d be just fine with you using it with a Kalita Wave or Origami pour-over dripper if you want. A long-press of the brew button also lets you choose between the default (4 ounces of water) bloom and a shorter (2 ounces) bloom, which is preferable if you are brewing a single cup.
All of the removable parts are hand wash-only, but I never found them needing more than a rinse between uses. The instructions recommend occasional cleaning and descaling with an approved solution to keep the lines clean though, which is important maintenance for any coffee maker.
It has an external, detached water tank that takes up more counter space than it would if it were flush with the machine, but that cuts both ways. I actually love that it’s connected via a sturdy-yet-flexible hose, allowing you to position it on either side of the machine in a variety of ways depending on your specific needs.
What we’d leave: Ratio is a brand known for machines with parts that feel very high quality, as senior editor Noah Kaufman has pointed out in his reviews of its other two machines. Some of the Ratio Four’s parts are definitely in line with that reputation, like the heavy braided hose between the brewer and water tank. But there are exterior parts of the brewer that do feel less substantial than you might expect for something that costs $279. I also found myself double checking that the filter basket was installed correctly, because it doesn’t click or snap to signal it’s on right.
“Set it and forget it” coffee drinkers should take note that the water reservoir isn’t “smart,” meaning it will brew whatever water is inside, so a full reservoir with a coffee mug underneath will overflow. If that’s something you don’t want to think about, the Cuisinart Custom Grind and Brew might serve you better as it requires less frequent refills.
