Kipling composed “If—” in iambic pentameter, a very traditional meter that consists of lines with five iambic feet. (Recall that an iamb is a metrical foot made up of one stressed syllable followed by a stressed syllable, as in the words “for-give” and “ex-cept.”) From sixteenth century on, iambic pentameter has been the meter of choice for poets with serious subject matter. The reason for this preference has primarily to do with line length. In English, lines with four feet or fewer tend to have a song-like meter, especially when the lines rhyme. By contrast, lines with five feet are just long enough to avoid having a sing-song quality, and instead give the verse a more refined feel. It’s for precisely this reason that iambic pentamer is sometimes referred to as a form of “heroic verse.” Heroic verse is so called because its refined, even noble sound lends itself to works of high seriousness. Kipling’s choice to write “If—” in iambic pentameter reflects this longstanding association with the meter’s noble sound. After all, the entire poem aims to advise a boy on how to achieve the nobility of spirit associated with traditional ideas of masculinity.

Though Kipling uses iambic pentameter throughout the poem, it’s worth noting a significant alteration he makes to this meter. Namely, he adds an extra syllable at the end of the first line in each line-pair. The technical term for this technique is hypercatalexis (HY-per-CAT-uh-LECK-sis). To see hypercatalexis in action, consider these lines from the second stanza (lines 9–12):

     If you | can dream— | and not | make dreams | your mas- | ter;   
         If you |can think— | and not | make thoughts | your aim;
     If you | can meet | with Tri- | umph and | Dis-as- | ter
         And treat | those two | im-pos- | tors just | the same.

Note how the first and third lines each consist of five iambic feet, followed by one extra unstressed syllable. By contrast, the second and fourth lines each consist of perfectly regular iambic pentameter. If you read these lines aloud, you’ll notice how the line break within each line-pair differs from the break between the two line-pairs. Because of the extra syllable, the pause in the middle of each line-pair is slightly shorter. It’s as if the extra syllable anticipates the continuation of the thought on the other side of the line break, urging the reader on. By contrast, the pause between line-pairs is longer, signaling a more definitive break between distinct thoughts. In this sense, the extra syllable functions a little like punctuation, subtly altering the meter and introducing a slight lilt to the poem’s overall rhythm.