Swim Race Time Predictor
Enter your CSS pace to estimate race times for 400m, 1500m, half Ironman (1900m) and Ironman (3800m).
Your Critical Swim Speed (CSS) is an excellent predictor of your racing potential. This predictor uses empirical reference data to estimate your race times across four key distances: 400m (pool), 1500m (open water / world championship), 1900m (half Ironman) and 3800m (Ironman). Predictions are given as a range (optimistic and conservative times) based on your CSS level. Simply enter your CSS pace per 100m to get your personalized estimates.
Enter your CSS pace
Your CSS (Critical Swim Speed) pace represents your swimming threshold. If you don't know it yet, use our CSS Calculator (/css) with 400m and 200m time trials. You can also use your T-pace or threshold pace from your GPS watch.
Format: M:SS (minutes:seconds) or seconds only
Full reference table
Estimated time ranges by CSS level and distance. Find your CSS in the left column to see your potential race times.
| Level | CSS /100m | 100m | 200m | 400m | 1500m | 1900m | 3800m |
|---|---|---|---|---|---|---|---|
10 | 1:10 – 1:15 | 0:55–1:02 | 2:00–2:15 | 4:20–4:40 | 17:30–19:00 | 22:30–24:30 | 47:00–51:00 |
9 | 1:15 – 1:20 | 1:00–1:07 | 2:10–2:25 | 4:40–5:00 | 19:00–20:15 | 24:30–26:00 | 51:00–54:00 |
8 | 1:20 – 1:25 | 1:04–1:12 | 2:20–2:35 | 5:00–5:20 | 20:15–21:45 | 26:00–28:00 | 54:00–58:00 |
7 | 1:25 – 1:30 | 1:08–1:17 | 2:30–2:46 | 5:20–5:40 | 21:45–23:00 | 28:00–29:30 | 58:00–1:02:00 |
6 | 1:30 – 1:35 | 1:13–1:22 | 2:40–2:57 | 5:40–6:00 | 23:00–24:30 | 29:30–31:30 | 1:02:00–1:05:00 |
5 | 1:35 – 1:40 | 1:17–1:27 | 2:50–3:08 | 6:00–6:20 | 24:30–25:45 | 31:30–33:00 | 1:05:00–1:09:00 |
4 | 1:40 – 1:45 | 1:22–1:32 | 3:00–3:20 | 6:20–6:40 | 25:45–27:00 | 33:00–35:00 | 1:09:00–1:12:00 |
3 | 1:45 – 1:50 | 1:26–1:37 | 3:10–3:32 | 6:40–7:00 | 27:00–28:30 | 35:00–36:30 | 1:12:00–1:16:00 |
2 | 1:50 – 1:55 | 1:31–1:42 | 3:20–3:44 | 7:00–7:20 | 28:30–29:45 | 36:30–38:30 | 1:16:00–1:20:00 |
1 | 1:55 – 2:00 | 1:37–1:50 | 3:34–4:00 | 7:20–8:00 | 29:45–32:30 | 38:00–41:00 | 1:20:00–1:26:40 |
Reference data inspired by Outpace Swimming (© 2020 Outpace Swimming, www.outpaceswimworkouts.com). 100m and 200m derived from swimming physiology ratios.