While I was baking yesterday, I used one of my measuring cups to measure some flour by weight, using my OXO kitchen scale. The scale is accurate. (I previously verified this using reference weights.) Next, I needed some water, and the measuring cup was still sitting on the scale, so I just poured the water into it. To my surprise, less water fit into the cup than I expected. I made a mental note to check on this, and here are the results… Below are the two sets of measuring cups I own. Both are metric sets, that is, 1 cup = 250 ml. Each set contains 1 cup, ½ cup, ⅓ cup, and ¼ cup measures. These are the actual volumes held by each set, with the percentage error. Stainless steel: 1 cup: 223 ml (–11%) ½ cup: 116 ml (–7%) ⅓ cup: 73 ml (–12%) ¼ cup: 56 ml (–10%) Plastic: 1 cup: 250 ml (0%) ½ cup: 135 ml (+8%) ⅓ cup: 91 ml (+9%) ¼ cup: 69 ml (+10%) Of eight measuring cups, only one is accurate. The others deviate by a whopping 7–12% from the nominal value. Imagine you go into a hardware store and buy a measuring tape. The tape works like this: when it tells you that something is 10 meters (or yards) long, the actual length can be anything from 8.8 meters to 12 meters (or yards), depending on which brand of tape you bought… I'd like to replace these cups with ones that are accurate. I don't need laboratory-grade perfection; something that's within 1–2% would be fine. But I don't know how to find such cups. I mean, it's awkward walking into a store, pulling out a kitchen scale and a bottle of water, and telling the shop assistant that "I need to check whether these work." At best, I'd get a long stare; it worst, they might politely show me the door. Does anyone know of accurate metric cup measures?