Units of Measure by weight and by volume

US fluid Units of Measure (by volume/capacity) (click on any column header to sort)
drop0.038507200114 16 drops = 1/8 teaspoon
teaspoon4.928921614586 3 teaspoons = 1 tablespoon
tablespoon14.786764843759 1 tablespoon = 3 teaspoons
ounce (fluid)29.573529687517 1 cup = 8 ounces
cup236.588237500136 1 cup = 16 tablespoons
pint473.176473000000 1 pint = 2 cups = 16 fluid ounces
quart946.352950000544 1 quart = 4 cups
liter1000.000000000000 1 liter = 0.264 gallons = 61.024 cubic inches
gallon3785.411780000000 1 gallon = 128 fluid ounces

Dry Units of Measure (by weight) (click on any column header to sort)
ounce (dry)28.349523100000  
pound453.592369600000 1 pound = 16 dry ounces
pint (dry)550.610471357500 1 dry pint = 33.6003125 cubic inches
quart (dry)1101.221000000000 1 dry quart = 67.2006 cubic inches
gallon (dry)4404.883770860000 1 dry gallon = one-eighth of a bushel
peck8809.768000000000 1 Peck = 8 Dry Quarts = 537.6 cubic inches

Measurements are based on either weight, or volume (capacity). There is no specific conversion between weight and volume unless you know the density of the ingredient. However, water, at 4 °C, is often used as a standard to derive the weight of a volume specification. For example, one cup of water (at 4 °C) weighs 236.588 grams. A cup of popcorn, of course, weighs much less (8 grams).

Here is the USDA list of Food Item Densities for one cup of selected food items.

Both liquid measure and dry measure have the same volume.

For the most precise measurements, weigh all ingredients with a scale.