The 300 meter hurdles and the 400 meter hurdles are closer than they look. Same barrier heights. Same 45 meters to the first hurdle, same 35 meters between every one after it. The 300 stops after eight barriers with 10 meters left to run. The 400 hands you two more and then a 40 meter sprint to the line. Nearly every US high school runs the 300, while the NCAA, USATF, and the rest of the world run the 400, which is why most college freshmen are learning a new race.
Measured from the gun, the hurdle positions are identical: 45 meters to the first, then 35 meters apart. Boys and men clear 36 inches in both races and girls and women clear 30 inches in both. The 300 ends after hurdle eight. The 400 puts hurdle nine at 325 meters and hurdle ten at 360, then makes you run 40 more. Heights for every hurdle event are tabulated in the hurdle height table by event.
The 300 packs the same opening into a race a developing athlete can finish without coming apart, and it ends on the home straight. NFHS raised the boys' barrier from 30 to 36 inches in 1984 and left the distance alone. Girls have contested it since 1981. Grade-by-grade times for the American race are in the 300m hurdle benchmarks by age.
The two extra barriers arrive exactly when your stride pattern is already failing, and the run-in quadruples. Most athletes add a stride or two between the late hurdles and have to learn to switch lead legs. Athletes who came out of the open 400 handle the jump better than pure sprint hurdlers do. Athletes coming out of the open 400 can check their baseline against what a good 400m time is.
The one skill that carries straight from the 300 to the 400 is holding a rhythm when you are tired. Film the last three barriers of any long hurdle rep and the AI counts your strides and shows you exactly where the pattern stretched.
Follow up in chat and ask questions. The AI remembers your analysis and speaks the language of hurdles coaching.
There is no official conversion. This is the estimate college coaches use when they recruit off a 300 time.
Recruiting conversions run off a best mark in decent conditions. A tired midweek dual-meet time will underestimate you by a second or more.
Men add roughly 14 to 17 seconds. Women add roughly 15 to 19. The faster you already are, the smaller the number you add.
If your open 400 is strong relative to your sprint hurdle time, take the low end. Sprint hurdlers moving up should take the high end, because the last 100 meters is where they give it back.
Sydney McLaughlin ran 38.90 for 300 hurdles and 53.82 for 400 hurdles in the same 2017 season, a gap of 14.92 seconds. That is close to the floor of what is possible.
The first year converts badly, because clearing hurdles nine and ten with a broken stride pattern is a learned skill. Judge the conversion in year two, not in September.
The two races share every measurement except the number of barriers and the length of the run-in.
| Spec | 300m hurdles | 400m hurdles |
|---|---|---|
| Who runs it | US high school, nearly every state | NCAA, USATF, World Athletics, Olympics |
| Number of hurdles | 8 | 10 |
| Start to hurdle 1 | 45 m | 45 m |
| Spacing between hurdles | 35 m | 35 m |
| Last hurdle to finish | 10 m | 40 m |
| Height, boys / men | 36 in (0.914 m) | 36 in (0.914 m) |
| Height, girls / women | 30 in (0.762 m) | 30 in (0.762 m) |
| Rough conversion, male athletes | your 300mH time | add about 14 - 17 s |
| Rough conversion, female athletes | your 300mH time | add about 15 - 19 s |
| HS national record | 34.72 boys (Andrew Jones, 2026)*, 38.90 girls (Sydney McLaughlin, 2017) | 49.38 boys (Kenneth Fergusson, 2002), 53.82 girls (Sydney McLaughlin, 2017) |
| World record or best | 32.67 men (Karsten Warholm, 2025)**, 36.86 women (Femke Bol, 2022)** (7 hurdles) | 45.94 men (Karsten Warholm, 2021), 50.37 women (Sydney McLaughlin-Levrone, 2024) |
Common questions athletes and coaches ask about this topic.
A directory of every hurdles page on the site, from broad analysis tools to specific phase deep-dives. Each entry points to a focused write-up.
Download the app. Film a rep. See what the AI sees. Free first analysis, no card, no account required.
