The IRONMAN 70.3 Weymouth 2026 pairs a sheltered 1.2 mile bay swim and a flat, fast 13.1 mile seafront run with a 56 mile loop through the rolling Dorset countryside north of town. Here's your course breakdown and Best Bike Split race plan for race day.
Weymouth has a reputation as one of the more scenic stops on the UK 70.3 calendar, and that reputation is deserved. It's also, quietly, one of the harder bike legs in the country. The loop north through Dorchester and up into the Dorset Downs isn't a series of monster climbs, it's a steady grind of short, punchy rises on narrow lanes that never really lets a rider settle into a rhythm. Athletes who treat that terrain like a flat time trial arrive at T2 with a bike split they're proud of and a run that falls apart by mile 6. The ones who pace it as one piece of a longer race tend to have the opposite day.
Race Overview
Weymouth has hosted IRONMAN branded racing for more than a decade, building on the town's legacy as a 2012 Olympic sailing venue. The race draws a field of roughly 2,800 athletes and has become a fixture for UK triathletes chasing a fast run course and a genuinely tough bike leg in the same day.
For 2026, the race is scheduled for Sunday, September 20, with transition and the race village based at Lodmoor Country Park and a 17 hour course time limit. The swim start is a rolling wave format organized by predicted pace, which keeps the sheltered bay from getting too congested at the gun.
Course Description
The swim covers 1.2 miles in Weymouth Bay, a naturally protected inlet that hosted Olympic sailing in 2012 and stays calm for a UK open water swim. It's a single loop laid out in a rectangle with right hand buoy turns, which rewards athletes who are comfortable sighting and breathing to their right. Water temperature in late September typically sits in the low 60s Fahrenheit, so the swim is reliably wetsuit legal. From the pebble beach exit it's a short transition to Lodmoor Country Park, where T1 happens on concrete.
The bike is where this course earns its reputation. It's a single anti-clockwise loop of 56 miles that heads north out of Weymouth through Dorchester before working through a string of Dorset villages, Godmanstone, Cerne Abbas, Piddlehinton, Puddletown, and out toward King's Stag, before looping back to the coast. The roads are narrow, exposed, and rolling almost the entire way, with pitches steep enough to hit grades above 12 percent in places. None of it is long enough to be classified a true climb, but the volume of short rises adds up, and there's very little flat ground to recover on between them. Reported elevation gain for the loop varies by source, from roughly 2,600 feet on the low end to closer to 4,600 feet on the high end, with GPS based estimates generally landing around 3,250 feet. Whatever the exact number, the course rides hillier than its billing suggests, and riders who show up expecting a fast, flat English coastal loop are usually surprised by mile 20.
The run is a 13.1 mile multi-lap course along Weymouth's seafront esplanade, starting near Lodmoor Country Park before settling into laps along the promenade in front of the finish area. It's flat, tarmac the whole way, and about as fast a half marathon course as UK racing offers, with aid stations spaced roughly every 2 kilometers and constant spectator contact on every lap. That flat, fast profile is exactly why the bike leg matters so much. There's nowhere on this run to hide a bike leg that was ridden too hard.
Forecasted Weather
Late September in Weymouth sits in a transitional stretch of English autumn. Daytime highs typically land in the mid 60s Fahrenheit, with morning temperatures at the start closer to the mid 50s. Cloud cover is common, with roughly half of days seeing mostly cloudy or overcast skies, and the chance of rain by this point in September climbs into the mid 20 percent range. Wind is the bigger factor for this course specifically, averaging around 13 to 14 mph out of the west, which adds real resistance on the exposed lanes north of Dorchester and can turn an already punchy bike leg into a longer day than the elevation numbers alone suggest.
Why This Course Rewards a Best Bike Split Plan
Weymouth gets sold on its scenery and its fast run course, and both are real. What doesn't get talked about enough is how easy it is to blow up a good day on the bike leg here. A BBS race plan for the 2026 IRONMAN 70.3 Weymouth will:
- Manage the short, repeated rises instead of surging each one. This course doesn't have one defining climb, it has dozens of small ones back to back on narrow lanes. A plan built around holding a target power through that terrain keeps a rider from spiking watts on every rise and paying for it late.
- Protect the run from the first mile of the bike. With a flat, fast run course waiting at T2, the temptation to ride Weymouth's hills hard is real. A plan built for the full race distance, not just a strong bike split, keeps enough in the legs to actually use that run course.
- Account for the wind exposure on the northern loop. The lanes past Dorchester and through the Dorset Downs are narrow and open, and a steady westerly adds resistance that doesn't show up in elevation data. Planning around that wind keeps effort honest on a course that already asks a lot.
- Plan fueling around the loop's aid station spacing. A hilly, technical 56 miles burns through fuel differently than a flat course does, and knowing where the checkpoints land on this specific loop keeps nutrition from becoming an afterthought on race day.
Interactive Race Plan and Course Map
This power plan was modeled for an athlete with an average CdA of 0.2864, an FTP of 300 watts and weighing 75 kg. Want to see what your time would be on the 70.3 Weymouth course? Try the Time Analysis feature below, where you can quickly adjust Drag, Power, Weight and Crr to your own values. Check out our demo race plan to see what a premium race plan looks like.
| Interval | Int. Time | Total Time | Int. Dist. | Total Dist. | Grade | Speed | Power |
|---|---|---|---|---|---|---|---|
| #1 | 00:05:45 | 00:05:45 | 3.37 km | 3.37 km | +0.33 % | 35.14 km/h | 227 w |
| #2 | 00:00:05 | 00:05:51 | 0.07 km | 3.44 km | +1.40 % | 40.86 km/h | 241 w |
| #3 | 00:04:57 | 00:10:48 | 1.73 km | 5.17 km | +5.10 % | 20.95 km/h | 281 w |
| #4 | 00:00:08 | 00:10:57 | 0.06 km | 5.23 km | +1.45 % | 26.40 km/h | 242 w |
| #5 | 00:00:31 | 00:11:28 | 0.44 km | 5.67 km | -5.90 % | 50.31 km/h | 135 w |
| #6 | 00:02:21 | 00:13:49 | 1.63 km | 7.30 km | -0.09 % | 41.64 km/h | 217 w |
| #7 | 00:00:51 | 00:14:41 | 0.36 km | 7.66 km | +4.10 % | 25.30 km/h | 273 w |
| #8 | 00:02:18 | 00:16:59 | 1.59 km | 9.25 km | -1.60 % | 41.45 km/h | 195 w |
| #9 | 00:00:57 | 00:17:57 | 0.55 km | 9.80 km | +1.59 % | 34.10 km/h | 244 w |
| #10 | 00:00:42 | 00:18:39 | 0.56 km | 10.36 km | -4.16 % | 47.92 km/h | 158 w |
| #11 | 00:01:08 | 00:19:48 | 0.62 km | 10.98 km | +2.49 % | 32.54 km/h | 258 w |
| #12 | 00:00:58 | 00:20:47 | 0.62 km | 11.60 km | -1.45 % | 37.86 km/h | 198 w |
| #13 | 00:00:11 | 00:20:58 | 0.11 km | 11.71 km | +4.57 % | 35.68 km/h | 277 w |
| #14 | 00:00:08 | 00:21:06 | 0.06 km | 11.77 km | +0.54 % | 24.87 km/h | 229 w |
| #15 | 00:00:37 | 00:21:44 | 0.50 km | 12.27 km | -5.07 % | 48.88 km/h | 149 w |
| #16 | 00:00:09 | 00:21:53 | 0.13 km | 12.40 km | +1.32 % | 52.17 km/h | 241 w |
| #17 | 00:01:21 | 00:23:14 | 0.57 km | 12.97 km | +4.18 % | 25.33 km/h | 312 w |
| #18 | 00:04:04 | 00:27:19 | 2.64 km | 15.61 km | -0.13 % | 38.75 km/h | 214 w |
| #19 | 00:00:23 | 00:27:43 | 0.34 km | 15.95 km | -6.57 % | 53.14 km/h | 134 w |
| #20 | 00:00:04 | 00:27:47 | 0.08 km | 16.03 km | -2.34 % | 59.92 km/h | 182 w |
| #21 | 00:06:34 | 00:34:22 | 4.02 km | 20.05 km | +0.10 % | 36.68 km/h | 223 w |
| #22 | 00:00:43 | 00:35:06 | 0.30 km | 20.35 km | +3.40 % | 24.96 km/h | 293 w |
| #23 | 00:01:19 | 00:36:25 | 0.81 km | 21.16 km | -1.45 % | 36.63 km/h | 207 w |
| #24 | 00:12:43 | 00:49:08 | 6.67 km | 27.83 km | +0.99 % | 31.47 km/h | 238 w |
| #25 | 00:02:32 | 00:51:41 | 1.72 km | 29.55 km | -1.41 % | 40.60 km/h | 197 w |
| #26 | 00:00:22 | 00:52:04 | 0.20 km | 29.75 km | +0.67 % | 31.15 km/h | 235 w |
| #27 | 00:00:17 | 00:52:21 | 0.20 km | 29.95 km | -3.98 % | 40.76 km/h | 163 w |
| #28 | 00:00:06 | 00:52:28 | 0.09 km | 30.04 km | -0.31 % | 45.12 km/h | 214 w |
| #29 | 00:01:06 | 00:53:35 | 0.59 km | 30.63 km | +1.85 % | 31.75 km/h | 251 w |
| #30 | 00:07:03 | 01:00:39 | 3.93 km | 34.56 km | +0.13 % | 33.40 km/h | 228 w |
| #31 | 00:03:15 | 01:03:55 | 1.55 km | 36.11 km | +1.61 % | 28.48 km/h | 249 w |
| #32 | 00:00:38 | 01:04:34 | 0.42 km | 36.53 km | -2.92 % | 38.68 km/h | 183 w |
| #33 | 00:08:30 | 01:13:04 | 4.56 km | 41.09 km | +0.63 % | 32.19 km/h | 234 w |
| #34 | 00:01:10 | 01:14:14 | 0.54 km | 41.63 km | +2.29 % | 27.51 km/h | 258 w |
| #35 | 00:05:43 | 01:19:58 | 2.81 km | 44.44 km | +1.52 % | 29.42 km/h | 246 w |
| #36 | 00:02:01 | 01:21:59 | 1.54 km | 45.98 km | -3.15 % | 45.75 km/h | 175 w |
| #37 | 00:03:08 | 01:25:08 | 1.96 km | 47.94 km | +0.15 % | 37.44 km/h | 223 w |
| #38 | 00:00:16 | 01:25:25 | 0.24 km | 48.18 km | -6.72 % | 51.39 km/h | 135 w |
| #39 | 00:01:31 | 01:26:56 | 0.84 km | 49.02 km | +1.30 % | 33.25 km/h | 242 w |
| #40 | 00:03:35 | 01:30:31 | 2.62 km | 51.64 km | -1.32 % | 43.86 km/h | 197 w |
| #41 | 00:01:32 | 01:32:03 | 0.65 km | 52.29 km | +2.35 % | 25.34 km/h | 261 w |
| #42 | 00:00:55 | 01:32:59 | 0.60 km | 52.89 km | -2.27 % | 38.77 km/h | 191 w |
| #43 | 00:00:05 | 01:33:04 | 0.06 km | 52.95 km | -5.94 % | 45.00 km/h | 144 w |
| #44 | 00:03:16 | 01:36:21 | 1.83 km | 54.78 km | +0.48 % | 33.59 km/h | 230 w |
| #45 | 00:01:26 | 01:37:47 | 0.78 km | 55.56 km | +1.12 % | 32.45 km/h | 241 w |
| #46 | 00:00:22 | 01:38:09 | 0.24 km | 55.80 km | -2.28 % | 39.32 km/h | 180 w |
| #47 | 00:02:33 | 01:40:43 | 1.24 km | 57.04 km | +2.38 % | 29.00 km/h | 258 w |
| #48 | 00:00:40 | 01:41:23 | 0.51 km | 57.55 km | -4.11 % | 45.21 km/h | 162 w |
| #49 | 00:01:33 | 01:42:57 | 0.86 km | 58.41 km | +1.72 % | 32.85 km/h | 247 w |
| #50 | 00:00:27 | 01:43:25 | 0.31 km | 58.72 km | -2.97 % | 40.85 km/h | 184 w |
| #51 | 00:01:44 | 01:45:09 | 1.01 km | 59.73 km | +0.86 % | 34.70 km/h | 234 w |
| #52 | 00:01:26 | 01:46:35 | 0.62 km | 60.35 km | +3.96 % | 25.90 km/h | 288 w |
| #53 | 00:01:05 | 01:47:40 | 0.67 km | 61.02 km | +0.01 % | 36.85 km/h | 218 w |
| #54 | 00:06:21 | 01:54:02 | 1.56 km | 62.58 km | +8.29 % | 14.72 km/h | 295 w |
| #55 | 00:01:03 | 01:55:05 | 0.51 km | 63.09 km | +1.69 % | 28.96 km/h | 252 w |
| #56 | 00:02:03 | 01:57:09 | 1.54 km | 64.63 km | -1.67 % | 44.94 km/h | 188 w |
| #57 | 00:01:13 | 01:58:23 | 0.75 km | 65.38 km | +1.32 % | 36.79 km/h | 242 w |
| #58 | 00:02:18 | 02:00:41 | 1.85 km | 67.23 km | -2.02 % | 48.10 km/h | 184 w |
| #59 | 00:00:52 | 02:01:34 | 0.45 km | 67.68 km | +2.53 % | 31.11 km/h | 261 w |
| #60 | 00:00:33 | 02:02:08 | 0.34 km | 68.02 km | -1.44 % | 36.58 km/h | 197 w |
| #61 | 00:00:25 | 02:02:33 | 0.37 km | 68.39 km | -4.66 % | 52.97 km/h | 152 w |
| #62 | 00:01:13 | 02:03:47 | 0.72 km | 69.11 km | +1.97 % | 35.22 km/h | 251 w |
| #63 | 00:00:05 | 02:03:53 | 0.05 km | 69.16 km | -1.14 % | 31.70 km/h | 195 w |
| #64 | 00:00:33 | 02:04:26 | 0.58 km | 69.74 km | -8.30 % | 62.03 km/h | 123 w |
| #65 | 00:00:34 | 02:05:01 | 0.59 km | 70.33 km | -3.05 % | 60.89 km/h | 164 w |
| #66 | 00:01:58 | 02:06:59 | 1.25 km | 71.58 km | +1.01 % | 37.92 km/h | 235 w |
| #67 | 00:00:09 | 02:07:09 | 0.10 km | 71.68 km | -2.00 % | 37.53 km/h | 185 w |
| #68 | 00:00:35 | 02:07:44 | 0.55 km | 72.23 km | -5.47 % | 56.08 km/h | 142 w |
| #69 | 00:01:23 | 02:09:07 | 1.20 km | 73.43 km | -2.26 % | 52.10 km/h | 179 w |
| #70 | 00:00:06 | 02:09:14 | 0.09 km | 73.52 km | -5.35 % | 52.19 km/h | 141 w |
| #71 | 00:00:09 | 02:09:24 | 0.14 km | 73.66 km | -1.21 % | 51.34 km/h | 196 w |
| #72 | 00:00:33 | 02:09:58 | 0.28 km | 73.94 km | +4.49 % | 29.71 km/h | 277 w |
| #73 | 00:01:51 | 02:11:49 | 1.36 km | 75.30 km | -1.60 % | 43.94 km/h | 188 w |
| #74 | 00:00:11 | 02:12:01 | 0.18 km | 75.48 km | -7.90 % | 54.64 km/h | 119 w |
| #75 | 00:00:23 | 02:12:24 | 0.25 km | 75.73 km | +4.51 % | 37.90 km/h | 283 w |
| #76 | 00:01:14 | 02:13:39 | 0.86 km | 76.59 km | -1.42 % | 42.02 km/h | 190 w |
| #77 | 00:00:06 | 02:13:45 | 0.09 km | 76.68 km | -4.33 % | 49.88 km/h | 152 w |
| #78 | 00:00:35 | 02:14:20 | 0.33 km | 77.01 km | +4.40 % | 33.86 km/h | 298 w |
| #79 | 00:00:11 | 02:14:32 | 0.09 km | 77.10 km | +0.39 % | 28.43 km/h | 223 w |
| #80 | 00:00:16 | 02:14:48 | 0.23 km | 77.33 km | -8.07 % | 49.16 km/h | 126 w |
| #81 | 00:00:05 | 02:14:54 | 0.09 km | 77.42 km | -2.07 % | 58.99 km/h | 182 w |
| #82 | 00:01:28 | 02:16:22 | 0.92 km | 78.34 km | +0.17 % | 37.35 km/h | 224 w |
| #83 | 00:01:11 | 02:17:33 | 0.58 km | 78.92 km | +3.31 % | 29.17 km/h | 270 w |
| #84 | 00:01:44 | 02:19:18 | 1.27 km | 80.19 km | -1.46 % | 43.77 km/h | 194 w |
| #85 | 00:00:05 | 02:19:23 | 0.07 km | 80.26 km | -4.46 % | 47.14 km/h | 152 w |
| #86 | 00:00:15 | 02:19:39 | 0.19 km | 80.45 km | +1.42 % | 43.45 km/h | 243 w |
| #87 | 00:01:18 | 02:20:58 | 0.48 km | 80.93 km | +5.21 % | 21.83 km/h | 285 w |
| #88 | 00:00:31 | 02:21:29 | 0.40 km | 81.33 km | -5.64 % | 45.82 km/h | 138 w |
| #89 | 00:00:35 | 02:22:04 | 0.40 km | 81.73 km | +2.63 % | 41.03 km/h | 261 w |
| #90 | 00:05:36 | 02:27:40 | 2.72 km | 84.45 km | +2.02 % | 29.07 km/h | 251 w |
| #91 | 00:01:29 | 02:29:10 | 0.41 km | 84.86 km | +6.90 % | 16.50 km/h | 288 w |
| #92 | 00:00:50 | 02:30:01 | 0.72 km | 85.58 km | -5.78 % | 51.03 km/h | 138 w |
| #93 | 00:00:03 | 02:30:04 | 0.06 km | 85.64 km | -9.63 % | 65.92 km/h | 53 w |
| #94 | 00:01:12 | 02:31:17 | 0.94 km | 86.58 km | -1.33 % | 47.02 km/h | 200 w |
| #95 | 00:00:23 | 02:31:40 | 0.36 km | 86.94 km | -6.91 % | 56.19 km/h | 131 w |
| #96 | 00:00:08 | 02:31:48 | 0.17 km | 87.11 km | -11.10 % | 71.82 km/h | 0 w |
| #97 | 00:05:37 | 02:37:25 | 3.82 km | 90.93 km | -0.75 % | 40.78 km/h | 208 w |
| Totals/Avg | 02:37:25 | 02:37:25 | 90.96 km | 90.96 km | -0.72% | 34.67 km/h | 229.25 w |
Climb Summary by Category
| Category | Climb Count | Total Time | Total Dist. | Avg. Time | Avg. Dist. | Avg. Grade | Avg. Speed | Avg. Power |
|---|---|---|---|---|---|---|---|---|
| Cat4 | 12 | 00:24:18 | 8.75 km | 00:02:01 | 0.73 km | 4.46 % | 25.83 km/h | 280 w |
| All Cats | 12 | 00:24:18 | 8.75 km | 00:02:01 | 0.73 km | 4.46 % | 25.83 km/h | 280 w |
| Climb | Start Time | Start Dist. | Duration | Distance | Speed | Power | Grade | Elevation Gain | Category |
|---|---|---|---|---|---|---|---|---|---|
| #1 | 00:05:51 | 3.44 km | 00:05:06 | 1.80 km | 21.10 km/h | 275 w | 4.80 % | 86.16 m | Cat4 |
| #2 | 00:13:49 | 7.30 km | 00:00:51 | 0.36 km | 25.30 km/h | 273 w | 4.15 % | 14.99 m | Cat4 |
| #3 | 00:21:53 | 12.41 km | 00:01:40 | 0.71 km | 25.67 km/h | 264 w | 3.62 % | 25.93 m | Cat4 |
| #4 | 00:34:22 | 20.07 km | 00:00:43 | 0.30 km | 24.96 km/h | 293 w | 3.40 % | 10.37 m | Cat4 |
| #5 | 01:45:09 | 59.75 km | 00:01:26 | 0.62 km | 25.90 km/h | 278 w | 3.96 % | 24.53 m | Cat4 |
| #6 | 01:47:41 | 61.04 km | 00:07:24 | 2.07 km | 16.76 km/h | 285 w | 6.37 % | 131.82 m | Cat4 |
| #7 | 02:09:24 | 73.70 km | 00:00:33 | 0.28 km | 29.71 km/h | 277 w | 4.49 % | 12.52 m | Cat4 |
| #8 | 02:12:01 | 75.52 km | 00:00:23 | 0.25 km | 37.90 km/h | 286 w | 4.57 % | 11.43 m | Cat4 |
| #9 | 02:13:45 | 76.72 km | 00:00:35 | 0.33 km | 33.86 km/h | 298 w | 4.40 % | 14.51 m | Cat4 |
| #10 | 02:16:55 | 78.68 km | 00:00:38 | 0.27 km | 25.64 km/h | 279 w | 4.05 % | 11.00 m | Cat4 |
| #11 | 02:19:39 | 80.48 km | 00:01:18 | 0.48 km | 21.83 km/h | 285 w | 5.21 % | 24.92 m | Cat4 |
| #12 | 02:25:35 | 83.61 km | 00:03:35 | 1.27 km | 21.28 km/h | 271 w | 4.45 % | 56.65 m | Cat4 |
Build your own personalized IRONMAN 70.3 Weymouth power plan today! Sign up for a free Athlete Basic account to get started with your athlete profile and bike setup, then grab the 70.3 Weymouth course to model your own race plan.
IRONMAN 70.3 Weymouth FAQs
Your target power depends on your FTP, body weight, bike setup, and finish time goal — not a generic number that applies to every rider. The variables that matter most are your current fitness, your aerodynamic position, and the specific demands of the IRONMAN 70.3 Weymouth course. The best approach is to build a personalized plan in Best Bike Split using your actual athlete profile — you'll get a segment-by-segment power target based on your specific inputs rather than a one-size-fits-all recommendation.
Every course is different and requires its own unique pacing plan. On a multi-loop course, fatigue and wind shift between laps and what felt comfortable early can become unsustainable later. On an out-and-back, headwind in one direction becomes tailwind in the other — an asymmetry a flat power target can't account for. On a point-to-point or single-loop course, you only get one pass at every section with no opportunity to recalibrate. When you create a Best Bike Split race plan for IRONMAN 70.3 Weymouth, we model the specific demands of that course so your pacing strategy reflects the race you're actually doing.
Significantly — and the effect varies depending on the course profile. On flatter courses, wind and aerodynamics become the dominant variables in your speed equation, more so than on courses where gradient naturally dictates effort. On climbing-heavy courses, your power-to-weight ratio and how you manage the descents matter most. A Best Bike Split race plan lets you model the specific conditions forecasted for IRONMAN 70.3 Weymouth, so your targets reflect what you'll actually face on race day rather than what the course looks like on paper.
It depends on the course and how well you pace it. Flat, fast courses offer genuine PR potential but only if you execute correctly — without terrain to naturally regulate your effort, going out too hard early is easy and costly. Technical or hilly courses reward smart segment-by-segment pacing over raw fitness. Either way, a physics-based race plan from Best Bike Split gives you a realistic split prediction based on your actual profile so you know before race day what a well-executed bike leg looks like for you specifically.
Yes — and this is one of the most underused features. Once you've built your IRONMAN 70.3 Weymouth race plan, you can export it directly to Zwift, TrainerRoad, or any ERG-mode trainer for indoor sessions, or push it to your Garmin, Wahoo, or Karoo for outdoor rides. Training on your actual race plan means you arrive at IRONMAN 70.3 Weymouth already knowing what your target effort feels like at every section of the course — not just what the number says on paper.
