There are two answers, and almost everybody gives one of them. Young men called as teaching missionaries serve 24 months. Young women serve 18 months. The Church’s own wording is “24 months for elders and 18 months for sisters”, and the difference is not a technicality — it is six months, a quarter of the whole thing.
Which is why “the two years” is such a common and such an unhelpful shorthand. Roughly a third of the missionaries serving at any time are sisters, and the phrase quietly writes every one of them out of the sentence.
The numbers, and who they apply to
- Elders— young men, called from age 18 — serve 24 months.
- Sisters— young women — serve 18 months.
- Service missionaries, who serve from home rather than being assigned away, serve up to the same lengths.
- Senior missionaries are the exception to all of it. Their assignments are shorter and far more variable, and are worked out with their own circumstances in mind rather than set by a single term.
When the clock actually starts
It starts when they report, not when the letter arrives. Between the call and the first day there is usually a stretch of several months of paperwork, medical appointments and waiting, and none of it counts toward the term.
Training comes first and its length depends on the assignment — a missionary learning a new language is in training considerably longer than one who is not — and it is part of the term rather than something before it. Then comes the assignment itself, and then a release date that was, in practice, fixed the day they reported.
What it looks like in weeks, which is the real question
Families rarely want the number of months for its own sake. What they are working out is how much of this there is going to be: how many Mondays with a letter in them, how long the shape of the week is going to hold.
In weeks it is this:
- 24 months is about 104 weeks. A letter a week, and you will receive somewhere near a hundred of them.
- 18 months is about 78 weeks— so near enough eighty letters.
That is a bigger body of writing than almost anybody expects. A hundred weekly letters, written by somebody between eighteen and twenty-one, is longer than most novels. It is also, in most families, the only sustained piece of writing that person will ever do about their own life while it is happening.
It is worth knowing the number early, because the letters accumulate far faster than anybody plans for and the decisions about keeping them are much easier made in month two than in month twenty-two. There is more on that in keeping the letters safe while they’re still out.
When it is shorter than the number
A great many missions do not run the full term, and this is the part of the answer that usually goes unsaid.
Missionaries come home early for health, for mental health, for family circumstances, and for reasons that are nobody else’s business. It is ordinary. It is also, for the person it happens to, very often experienced as a failure — which is a thing worth knowing before you ask somebody how long they served and watch them decide how to answer.
The length is not the measure
Fourteen months is not most of a mission the way three-quarters is most of a pie. It is fourteen months of a person’s life, lived completely, and the record of it is exactly as complete as anybody else’s: the same weekly letters, the same photographs, the same people and places. A shorter mission produces a shorter record and nothing else about it is diminished.
If that is your family, there is a guide written specifically for it — when a missionary comes home early.
What the length means for the people at home
Two years and eighteen months feel different from the other end, and it is worth saying plainly what each one is.
- It is long enough for the person to change. The missionary who comes home is recognizably not the one who left, and the letters are the only continuous record of how that happened. Nobody notices it week to week; everybody notices it reading them end to end.
- It is long enough to forget the beginning. By month twenty, the first area is genuinely hazy for everybody involved, including them.
- It is short enough that it ends suddenly.The weekly rhythm that organized two years of a family’s Mondays stops on a specific date, and a lot of families are surprised by how much they miss it.
The short version
- Elders: 24 months. Sisters: 18 months. Both are full missions.
- Senior missionaries are different and far more variable.
- That is roughly 104 or 78 weekly letters, which is more writing than most people expect.
- A mission that ends early is a shorter record, not a lesser one.