When you are submitting a file for translation, you want to know how much it will cost. For translation between Japanese and English, it used to be the norm to calculate the cost on a page basis. One page of Japanese was taken as 400 characters and one page of English as 200 words. There are still companies who calculate costs in this way, however, the majority of translation agencies I work for, and my own office, calculate the cost on a per character/word basis.
So what it counted? The number of source language characters/words, or the number of characters/words in the completed translation? It depends. When I started working as a translator, the agencies that sent me work calculated the cost on a target language basis. This meant that neither the customer, nor I, the translator, knew the actual cost of the translation before it was finished. The client was given a rough estimate, and only found out the actual cost when the translation was finished. In Japanese to English translation, 400 characters is said to correspond to 200 English words, but this is just a guide. With this method of calculation, the exact cost depends on the style of writing of the translator. Some write clearly and concisely, others less so.
When I started my translation office, and began to get clients, the first question they asked was “How much will this cost?” Even now, this is always the first question my clients ask. So that I can give them an accurate answer, right down to the last character, I calculate the cost by counting the characters in the source text, that is, the Japanese document they give me, and provide an estimate based on that. The client knows exactly what he or she will pay once the job is finished. There is no ambiguity.
If you are requesting a translation, I recommend you ask the company or translator to calculate the cost on a source text basis. This way, you won’t have any surprises when the translation is delivered.