How this calculator works
For buying candy, estimate the number of visitors and multiply by the sweets you hand to each. Decorations and weather pull that estimate up or down: a house with lights and props attracts more children, and a storm keeps them home. For a container, the volume is simple geometry, but candies do not fill every corner. Equal spheres packed at random fill about 64 percent of a volume, so the usable space is the container volume times the fill level times 0.64, divided by the volume of one candy. Wrapped sweets and irregular shapes pack differently, so the answer is an estimate rather than a count.
Formula
attendance = expected children x decoration factor x weather factor. candies needed = attendance x candies per child, rounded up. packs = candies / pack size, rounded up. Container volume: cylinder = pi x (diameter / 2)^2 x height, rectangular = length x width x height, sphere = pi x diameter^3 / 6, quart jar = 0.946 L. candies that fit = floor(volume x fill x 0.64 / candy volume).
Worked example
Thirty children, normally decorated and pleasant weather gives 30 x 1.0 x 1.0 = 30 children. At three candies each that is 90 candies, so 3 packs of 30. A grandly decorated house during extreme weather expects 30 x 1.2 x 0.5 = 18 children, or 54 candies, which is 2 packs of 30. A cylindrical bowl 20 centimetres across and 20 centimetres tall holds 6.283 litres; at 80 percent full and a 1 cubic centimetre candy, it holds floor(6.283 x 0.8 x 0.64 / 0.000001) = 3,216 candies.
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Frequently asked questions
How many candies should I give each child?
One to three is common. Three keeps the visit cheerful without exhausting your supply, and a smaller number lets you serve more children. If you expect a large crowd, hand out one or two.
Why only 64 percent of the container?
That is the random close packing fraction for equal spheres. Candies are not perfect spheres and wrappers add friction, so real packing ranges roughly from 55 to 65 percent depending on shape.
How do decorations change attendance?
Houses with visible decorations tend to attract more children, while a dark house may be skipped. The factors here are rough rules of thumb, not measurements, so adjust them if you know your street.
Does weather really halve the visitors?
Heavy rain or extreme cold can cut attendance sharply, and the 0.5 factor is a rough allowance. Mild weather has little effect, which is why the pleasant and manageable options are close to one.