Boston Marathon
The oldest annual marathon. Cool spring conditions, qualifying-only field, downhill quad-trashing first half, Newton Hills back half.
Boston is cool but not low-sodium. Your sweat sodium concentration is fixed, so salty sweaters still need 500 to 800 mg per hour even at 50F. Target 16 to 20 oz of fluid per hour, resist overdrinking in the downhill first 10 miles (the leading hyponatremia cause here), and pre-dose 600 mg sodium 60 minutes before the start.
Boston Fueling Plan
For a 165 lb athlete finishing Boston in about 3 hr 30 min, plan roughly 75 g of carbs, 450 mg of sodium (600 mg for a salty sweater) and 450 ml of fluid per hour. That is about 260 g of carbs and 1,600 mg of sodium across the race.
| Finish time | Carbs | Sodium | Fluid |
|---|---|---|---|
| Front of field2 hr 45 min | 75 g/hr210 g total | 450 mg/hrsalty sweater 600 mg | 450 ml/hr1.2 L total |
| Mid-pack3 hr 30 min | 75 g/hr260 g total | 450 mg/hrsalty sweater 600 mg | 450 ml/hr1.6 L total |
| Back of pack4 hr 30 min | 75 g/hr340 g total | 450 mg/hrsalty sweater 600 mg | 450 ml/hr2 L total |
Computed by the free sodium and carb calculators for a 165 lb athlete in cool conditions. Fluid is a planning figure for what to carry, not a drinking schedule: on the day, drink to thirst. Your own numbers move with body weight and sweat rate.
Where The Sodium Math Bends
Boston starts at its high point, 475 ft, and finishes at 16 ft, a net drop of 459 ft. Cramping tends to cluster on the long climbs and the descents that follow them.
- Mile 0, Start, Hopkinton, 475 ft
- Mile 2, Ashland, 302 ft
- Mile 5, Framingham, 191 ft
- Mile 9, Natick, 149 ft
- Mile 12, Wellesley, 143 ft
- Mile 16, Newton Lower Falls, 53 ft
- Mile 18, West Newton, 142 ft
- Mile 21, Top of Heartbreak Hill, 228 ft
- Mile 24, Brookline, 30 ft
- Mile 26.2, Finish, Boylston Street, 16 ft
| Climb | Miles | Gain | Avg grade |
|---|---|---|---|
| Natick rise | 9 to 11 | 42 ft | 0.4% |
| Newton hills: Lower Falls to West Newton | 16 to 18 | 89 ft | 0.8% |
| Newton hills: mile 19 to 20 | 19 to 20 | 35 ft | 0.7% |
| Heartbreak Hill | 20 to 21 | 85 ft | 1.6% |
Source: B.A.A. 2026 Boston Marathon media guide, mile-by-mile course elevations
What's On Course
Water and Gatorade Endurance Formula (lemon-lime) are served at fluid stations about every mile from mile 2. Maurten Gel 100 and the caffeinated Gel 100 CAF 100 are handed out at three depots, and no food is listed on course. Official timing stops at 5:30 PM, about six hours after the last runner starts, and roads begin reopening behind a 13:44 per mile pace.
| Mile | Station | Cutoff |
|---|---|---|
| 11.8 | Gel depot, Wellesley town lineMaurten Gel 100 and Gel 100 CAF 100 | |
| 17 | Gel depot, NewtonMaurten Gel 100 and Gel 100 CAF 100 | |
| 21.5 | Gel depot, just past Boston CollegeMaurten Gel 100 and Gel 100 CAF 100 | |
| 26.2 | Finish, Boylston Street | Official timing stops 5:30 PM |
Source: B.A.A. course information and 2026 race guides, 2026
40-65°F · moderate humidity
Climate
cool
Humidity
moderate
Cutoff
6h after final wave start
10-yr avg high
58°F
10-yr avg low
39°F
Record high / low
82° / 29°F
Years with rain
80%
The Cumulative Deficit Window
Boston is a cool-weather marathon where the standard advice ("you need less sodium when it is cool") is wrong for a large fraction of the field. BAA qualifiers are typically lean, well-trained, and high sweat-rate athletes. Many of them are also salty sweaters. The Newton Hills late in the race (miles 16 to 21) are where sodium-driven cramping most often hits, particularly the climb up Heartbreak Hill. Most athletes overdrink water in the first 10 miles when they feel cool, then run a sodium deficit into the back half.
Key Considerations
- Salty sweaters should treat Boston like a warmer race for sodium intake. Cool ambient temperature does not lower sweat sodium concentration.
- The downhill first 16 miles is deceptively heat-generating; quad work raises core temperature regardless of air temp.
- Hyponatremia risk is real at Boston due to ambitious mid-pack runners drinking aggressively in cool weather. Stick to fluid targets.
- Pre-race sodium loading the night before (salty dinner) supports plasma volume before a cool-weather start when thirst signals are blunted.
Who Finishes, And How Fast
Official 2026 results
Men winner · 2026
John Korir
2:01:52KEN, course record
Women winner · 2026
Sharon Lokedi
2:18:51KEN
Finish rate ~97%
See The Full Boston Strategy Playbook
Course segments, pacing bands, and a race-day execution guide.
Free Tools, Pre-Filled For Boston
Tap any tool. We pre-load your event, climate, and sweat profile. Adjust your weight and finish target and the plan generates instantly.
Sodium plan
Per-hour sodium and fluid targets for Boston conditions.
Carb fueling
Hourly carb targets and a fuel menu calibrated to your weight and the Boston duration.
Heat protocol
10-14 day adaptation plan if you're racing into a warmer climate.
Hydration audit
Weigh-in test that converts a 60-minute training session into a measured sweat rate.
Caffeine timing
Pre-race dose, mid-race top-ups, and race-week taper protocol for Boston timing.
Dig Into The Science
Sodium Calculator for Endurance Athletes (Free Tool)
Sweat sodium varies 3 to 4x across athletes. A free sodium calculator that sets an hourly target from your body, sweat history, and race-day climate.
Stop Leg Cramps: Supplement Protocol & Risk Calculator
Leg cramps have two causes: electrolyte depletion and neuromuscular fatigue. Score yours with the free calculator, then load the 5 supplements that fix both.
Why Endurance Athletes Need More Carbohydrate
Carbohydrate is the limiting fuel for endurance. Why glycogen runs the show, grams per hour by duration, and how to train your gut to take more.
Your Boston Plan,
Built From Real Data.
Pro unlocks a per-leg sodium, fluid, and carb schedule keyed to the actual course: Hopkinton to Wellesley, Wellesley to Heartbreak Hill, and Heartbreak Hill to Boylston, dosed to pre-load sodium before the Newton Hills climb.
- Your sweat rate, from a weigh-in test or your best estimate
- Per-leg sodium, fluid, and carb schedule keyed to the course profile
- Branded, printable PDF
- Post-race feedback capture so the next plan is sharper
Per race
Every race
Unlimited race plans today. Strava connection and the multi-event calendar are still in development.
Free tools stay free, always
About Boston
Do I need less sodium because Boston is cool?
Not necessarily. Your sweat sodium concentration is a fixed individual trait. Cool weather lowers total sweat volume but does not change the mg per liter you lose. If you are a salty sweater, your hourly target stays high even at 50F.
When in the race should I take my pre-loaded sodium?
A 600 mg dose 60 minutes before the start, paired with 16-20 oz of fluid, supports plasma volume through the first hour. The first on-course intake should happen within the first 30 minutes of running, before thirst signals appear in cool conditions.
How much fluid should I take in cool Boston weather?
For most athletes targeting a sub-4 hour finish, 16 to 20 oz per hour is the working window. Resist the urge to drink at every water stop in the first 8 miles; cool-weather overdrinking is the leading hyponatremia cause at Boston.