What is Jim's age in "The Gift of the Magi"?

Towards the end of the story, Jim's age is mentioned when he returns home late from work. O. Henry writes that Jim looked thin and serious when he entered the apartment before mentioning that he was only twenty-two-years-old, which is a rather young age to have such weighty responsibilities. Although Jim is young, he is portrayed as a hard-working, industrious man, who goes to great lengths to make ends meet and to purchase the perfect Christmas present for his wife, Della. At the beginning of the story, the reader learns that Jim's salary has been reduced to twenty dollars per week and that there is only $1.87 to his wife's name, which is not enough to buy him a valuable Christmas present. While Della ends up selling her long, beautiful hair for money to purchase Jim a new fob for his gold watch, Jim ironically sells his valuable watch for money to purchase an expensive set of bedazzled combs for his wife's hair.

Jim may be 22 years old, but his physical appearance suggests a man who's old before his time. His surname, Young, is therefore somewhat ironic. A life of poverty, struggle, and hardship has had a disastrous effect on Jim. The shabby clothes he wears and his worn, haggard expression are indicative of a man comprehensively defeated by life. He didn't have much to begin with in terms of money or possessions, but since being forced to take a $10 a week cut in salary, he has even less. Money's too tight to mention, so if Jim's going to buy Della a Christmas gift he's going to have to make sacrifices. Hence his decision to sell his treasured pocket-watch to buy Della a fancy set of combs for her beautiful hair.

In the short story “The Gift of the Magi,” by O. Henry, Jim is 22 years old.

We are not told Jim’s age until about half way through the story. We can surmise that he and Della are rather young, though. He does not make much money and they do not have any children, both making it likely that they are young. However, we do not have to guess at Jim’s age. We are specifically told that he is 22. This happens when he comes home after Della has cut her hair to buy him his present. It is the first time he is actually present in the story. At that point, we are told

Poor fellow, he was only twenty-two--and to be burdened with a family!

From this, we can tell that Jim is 22 years old in this story.

The answer to your question can be found in the middle of this story, after Della has had her beautiful hair cut off and is waiting for Jim to enter their appartment and is hoping that Jim will not be to angry about her new look now that she has short hair. As Jim enters the appartment, we are given a description of his physical state and presentation:

The door opened and Jim stepped in and closed it. He looked thin and very serious. Poor fellow, he was only twenty-two--and to be burdened with a family! He needed a new overcoat and he was without gloves.

Thus we can see that Jim is twenty-two, and that he gives every appearance of having to struggle to make ends meet, as his frayed and old overcoat and his lack of gloves obviously suggests. In addition, his thin and serious nature likewise indicates the way in which he has to work so hard and try to support both himself and his wife.

What does Jim look like in "The Gift of the Magi"?

After Della sells her hair and uses the money to purchase a beautiful watch chain for her husband, Jim, he returns home. The narrator tell us,

He looked thin and very serious. Poor fellow, he was only twenty-two—and to be burdened with a family! He needed a new overcoat and he was without gloves.

In other words, then, Jim is rather slight. His physical thinness is, perhaps, a symptom of his salary being cut from $30 to $20 per week (which we learned early in the story). He also appears to be very serious, despite his relatively young age. This is likely also linked to his reduced salary, as this has clearly taxed his household (and his wife), requiring a degree of parsimony they never experienced when he earned more. The fact that Jim has a wife to support—a responsibility to her—seems to have taken its toll on him. In addition, important articles of winter clothing are either in bad shape or are missing completely: Jim seems to appear the way Della felt at the beginning of the story.

In "The Gift of the Magi" O. Henry doesn't describe Jim's appearance in that much detail, certainly not by comparison with his wife, Della. However, we are given some idea of what he looks like when he returns home after work on Christmas Eve. As Jim walks through the door he's described as being very thin. This could well be significant—a suggestion that perhaps he doesn't get enough to eat, what with his only making $20 a week.

It's notable that he isn't smiling, either. This could also be related to his low-paid job. Here's a young man of only twenty-two, and he has a family to take care of; the weight of the world appears to be on his shoulders. And those shoulders of his need to have a new coat on them, as the one he's wearing is way too old. From the scant information we're given, it's reasonable to infer that Jim appears prematurely aged by the privations that he and Della are forced to endure on a daily basis.