"Рассчитывать", "подсчитывать" -- what is the difference?

Question

"Рассчитывать", "подсчитывать", what is the difference ? I tried to distinguish them with their roots (раз- out in all directions and под- approach; coming "up to") but even then, they still both translate as "count"/"count on" to me.

Answer 1

Both verbs can be translated as "to count" or to "calculate", but "подсчитывать" is closer to count some finite amount of items - when, for instance, one is counting the number of shells, it's "подсчитать количество ракушек" and never "рассчитать". When it's about more complicated calculations, it's usually "рассчитывать"/"раcсчитать", like in "рассчитать, c какой скоростью нужно бросить камень" - "подсчитать" here will sound unnatural.

Also, only "рассчитывать" can be used in a meaning similar to "you can count on me" (ты можешь рассчитывать на меня").

Answer 2

"Рассчитывать" has two meanings. First is "to rely" or "will expect to" or "to expect" as "рассчитывать на что-то (на кого-то)". Second meaning is not about counting but about calculation. "Подсчитывать" mainly about very simple arithmetic.

Answer 3

"count on" (rely on) goes only for "рассчитывать". It also has other indirect meanings (e.g. "sack/fire smb", not widely used though).

Also "рассчитывать" means more work, more sophisticated work (more "calculate" than count"), and also planning / prediction.

Researches calculated the probability of... - Учёные рассчитали вероятность... (referring to a difficult task). Нужно рассчитать, сколько воды нужно взять - planning, if you go for a hike. Я всё рассчитал, мы выплатим кредит за два года - planning again.

"Подсчитать" is more day-to-day, simple work (counting), and also refers to results or current situation. Мы подсчитали наши расходы - the expences we already have Мы подсчитали голоса - it's a simple count. I cannot think of an example, where you cannot say "посчитали" instead of "подсчитали", although, "подсчёт голосов / очков" (counting votes / scores) are set expressions.