The formula
hours = sum of the guided hours of each level × distance factor
Where it comes from
The hours per level are published by Cambridge and the Instituto Cervantes, and they grow as you climb: the first levels cost ninety or a hundred hours, and from B1 on it is two hundred each. These are guided learning hours, on the assumption that you also study on your own; without that outside work, the figure falls short.
How to work it out by hand
- Add up the hours of each level you still have to go through
- Multiply by the distance factor of that language from yours
- Divide by the class hours you do each week
- That gives the weeks, and dividing by 4.3, the months
What is worth knowing
The distance between languages changes the answer more than anything else. The US Foreign Service Institute groups languages into four categories by what they cost an English speaker: between the closest and the furthest there is a difference of almost four times, which is why it is a field here. For an English speaker, Spanish and French sit in the first group, German in the second, and Arabic, Chinese or Japanese in the last. And a warning about pace: four weekly hours well spread out do more than a weekend marathon, because learning a language depends on frequency more than on the length of each session.