Why 1:15 for pour over
Pour over brewers like the V60 and Chemex drip fresh water through the grounds continuously, which extracts efficiently. That efficiency is why the standard ratio is 1:15, a touch stronger than drip's 1:16. The steady flow of fresh water keeps pulling flavor out, so you need slightly more coffee relative to water to keep the cup balanced.
Paper filters also remove oils that a French press keeps, which makes pour over taste cleaner and brighter but thinner in body. The 1:15 ratio compensates: it builds enough dissolved coffee to keep the clean cup from tasting watery.
Worked example 1: a 300 ml mug
Three hundred milliliters of water divided by 15 gives 20 grams of coffee, about 2.7 tablespoons. This is the single-cup dose to memorize: 20 grams in, 300 grams out. Grind medium-fine, like table salt. Heat water to 195 to 205 F, wet the filter first to rinse paper taste, add the grounds, and bloom with 40 to 50 grams of water for 30 to 45 seconds.
Then pour in slow spirals, keeping the water level steady, until you hit 300 grams total. Aim to finish pouring by about 2:00 and let it draw down by 3:00 to 3:30. If the bed finishes draining much faster, the grind is too coarse; much slower, too fine.
Worked example 2: 500 ml for two
Five hundred milliliters divided by 15 gives 33.3 grams of coffee, about 4.4 tablespoons. The technique is the same, just scaled: bloom with 60 to 70 grams of water, then pour to 500 grams total. Expect a slightly longer drawdown, 3:30 to 4:00, because the deeper bed drains more slowly.
For bigger brews, grind a touch coarser than your single-cup setting. The deeper coffee bed already slows the flow; keeping the single-cup grind would over-extract. This is the one adjustment most people miss when scaling up pour over.
Worked example 3: a 750 ml Chemex
A 6-cup Chemex brews about 750 milliliters. Divide 750 by 15 to get 50 grams of coffee, about 6.7 tablespoons. Chemex filters are thicker than V60 filters, so they drain slower and produce an exceptionally clean cup. Grind medium-coarse for Chemex, a step coarser than a V60, to keep the drawdown in the 4:00 range.
The thicker filter also means Chemex tolerates, and often rewards, a slightly stronger ratio. If 1:15 tastes thin through a Chemex, try 1:14 (53.6 grams per 750 ml) before changing the grind. The coffee ratio calculator has a pour over mode that converts any brew size to grams and tablespoons.
Dialing in: sour versus bitter
Sour, salty, or thin tasting coffee is under-extracted: tighten the ratio toward 1:14 or grind finer. Bitter, harsh, or drying coffee is over-extracted: loosen toward 1:16 or grind coarser. Change only one thing per brew, and give each change two brews before judging, since technique varies day to day.
Water temperature is the third lever. Below 195 F, extraction stalls and the cup tastes sour no matter the ratio. Above 205 F, bitterness climbs. If you do not have a thermometer, boil the water and wait 30 to 60 seconds; that lands in the right window for most kettles.
Pour over versus drip ratio
Automatic drip machines typically run at 1:16, slightly weaker than pour over's 1:15, partly because their shower heads wet the bed less evenly and their brew temperatures run cooler. If you are converting a drip recipe to pour over, use a little more coffee than the bag suggests, and if you are going the other way, a little less. The one-point difference is small but noticeable side by side.