How many cups is 100g of quinoa (uncooked)?

100g of quinoa (uncooked) (quinoa) is

½ cup + 1 tbsp

That's 0.59 US cups, 0.56 metric cups, or 9 level tablespoons.

Worked out from 1 US cup = 170g. Cups are rounded to the nearest kitchen fraction, with what's left over in level tablespoons. If you have scales, weighing is more accurate.

Other amounts of quinoa (uncooked)

200g: 1 cup + 3 tbsp
250g: 1½ cups
1 cup: 170g
Half a cup: 85g
A quarter cup: 43g
1 tablespoon: 11g
Full table for quinoa (uncooked)

Where these numbers come from

USDA FoodData Central, SR Legacy, food 20035: “Quinoa, uncooked”. USDA lists these household measures for it:

1 cup = 170g

Fractions of a cup are the cup weight scaled down. The tablespoon figure is the cup weight divided by 16, since USDA doesn't list a tablespoon for this ingredient. The teaspoon is a third of the tablespoon. Metric-cup figures assume a 250ml cup, and Australian tablespoons hold 20ml. Weights under 10g are rounded to 0.1g, everything else to the nearest gram. Full source list.