Sub-3:45 Marathon — Training Paces and Fitness Profile
Sub-3:45 marathon is meaningful competitive fitness — well into the upper tier of recreational marathon runners. Getting here requires consistent volume, real long runs, and structured quality work over one or more training cycles.
Quick answer: To break Sub-3:45:00 in the Marathon (RPI 41), your training paces are: easy 9:43/mi, threshold 7:40/mi, interval 6:42/mi. Equivalent fitness: Half Marathon 1:48:35, 10K 48:58.
Training paces for Sub-3:45:00 Marathon
RPI 41 · Goal: 3:44:59 · All paces in min/mile
Calculated from Daniels/Gilbert oxygen cost equations. Easy pace means "this pace or slower."
Equivalent race fitness
These are the predicted equivalent times at other distances for a runner with RPI 41 — assuming comparable training for each distance.
Half Marathon
1:48:35
8:17/mi
10K
48:58
7:53/mi
5K
23:36
7:36/mi
Training approach for Sub-3:45:00 Marathon
For sub-3:45 marathon, the primary training levers are 18–20 mile long runs at easy pace and one threshold session per week. Marathon-pace miles added to the end of long runs are the most race-specific preparation. Total weekly volume of 30–45 miles with one threshold session is the effective structure for this standard.
Calculate your current training paces
The table above shows paces for Sub-3:45:00 Marathon fitness. Enter your current race time to see where you are now and how far from the goal you sit.
Training Pace Calculator
These paces are based on your race time — not your body
The Daniels/Gilbert formula predicts training zones from a single race result. StrideIQ goes further: it tracks how your body specifically responds to threshold and interval work — which sessions produce your biggest gains, how quickly you recover, and when your fitness is peaking. Population formulas start the conversation. Your individual response data finishes it.
Common questions
What training paces should I use to target sub-3:45 in the marathon?
For sub-3:45:00 (3:44:59): Easy 9:43/mi, Marathon 8:08/mi, Threshold 7:40/mi, Interval 6:42/mi. RPI 41. Marathon training pace (8:08/mi) is what you practice in the final miles of long runs when your legs are already tired. Easy pace (9:43/mi) is where all other running happens.
What is the biggest training error for sub-3:45 marathon runners?
Not running enough miles at genuinely easy pace. Runners who target sub-3:45 often run 3–4 days per week but keep all runs at moderate effort. Slowing easy days to 9:43/mi or slower (which often feels too slow) allows recovery and enables the occasional hard session to generate real adaptation. Adding a 5th easy run often produces more improvement than making existing runs harder.
What half marathon corresponds to sub-3:45 marathon fitness?
Sub-3:45 marathon fitness (RPI 41) projects to approximately 1:48:35 half marathon potential. If you have run a half marathon near this time recently, you have the aerobic capacity for a sub-3:45 marathon — with 20-mile long runs and full marathon preparation.
Other goal pace guides
Paces calculated using the Daniels/Gilbert oxygen cost equations (1979). All values derived from the same formula used by the StrideIQ training pace calculator. Goal times use the target-minus-one-second convention (e.g., sub-20 = 19:59 input).