20-week marathon training plan

A 20-week marathon training plan takes a club runner on 45 km a week with a 1:55 half marathon from where they are to race day in 21 weeks, building to 79 km in the biggest week. It spends 8 weeks in base, 8 weeks in build, 2 weeks in peak, 2 weeks in taper, with 4 lighter weeks to absorb the work, on 6 days a week.

Build my marathon plan — free

Built from your own numbers and your own week. The first week is free.

Is 20 weeks enough?

20 weeks is a comfortable length for a marathon. There is room for a proper base before the harder work, lighter weeks to absorb it, and a taper that leaves you fresh rather than flat.

What the weeks are for

Base	8 weeks — aerobic volume, mostly easy, the foundation everything else stands on
Build	8 weeks — the harder sessions arrive and volume keeps climbing
Peak	2 weeks — the biggest, most race-specific weeks
Taper	2 weeks — volume drops, intensity stays, you arrive fresh
Lighter weeks	4, roughly every fourth week
Total	1213 km, 161 hours

The 21 weeks

Generated for a club runner on 45 km a week with a 1:55 half marathon.

Week	Phase	Volume	Load
1	Base	45 km	258
2	Base	48 km	276
3	Base	51 km	293
4	Base · down	35 km	203
5	Base	54 km	307
6	Base	57 km	325
7	Base	60 km	338
8	Base · down	41 km	239
9	Build	59 km	362
10	Build	62 km	376
11	Build	65 km	394
12	Build · down	47 km	279
13	Build	68 km	408
14	Build	71 km	426
15	Build	74 km	441
16	Build · down	54 km	311
17	Peak	77 km	447
18	Peak	79 km	459
19	Taper	66 km	375
20	Taper	51 km	292
21	Race · race	47 km	407

The biggest week, session by session

Week 18, peak phase — the heaviest week of the block.

Monday	Easy run — 1h12, 10.4 km
Tuesday	Threshold — 2 × 10 min — 0h54, 8.1 km
Tuesday	Strength — lower body — 0h27
Wednesday	Easy run — 1h12, 10.4 km
Friday	Race pace — 9 km — 1h12, 11.4 km
Saturday	Easy run — 1h12, 10.4 km
Sunday	Long run with a fast finish — 3h00, 28.1 km

The paces

Pace band	Per kilometre
Easy — the ceiling, not the target	6:19
Marathon pace	5:41
Threshold	5:22
Interval (VO₂max)	4:51

Computed from VDOT 38.3, derived from that time trial using Jack Daniels' model. Your own numbers will differ — the plan builds these from a time trial you enter.

What this plan says out loud

Worth knowing

Some sessions have been cut to fit the time you said you have — 75 minutes on a weekday and 180 at the weekend. That is a real constraint and the plan respects it, but be aware the long session is the one that matters most: if you can find more time anywhere, find it on the weekend.

Worth knowing

On 6 days a week there is nowhere to put 34 km without prescribing runs nobody should be doing. The plan caps individual easy runs at 14 km and carries less volume than your target as a result. More days would do more for you than longer runs.

Worth knowing

Race day looks like about 3:57:48 on today's fitness — Run 3h 58. Assumes a flat course, reasonable conditions and a sensible first half.

Common questions

Is 20 weeks enough for a marathon?

Yes, for most people who already exercise. We would choose at least 16 weeks, and this is 20.

How many days a week does it train?

6, on Monday, Tuesday, Wednesday, Friday, Saturday, Sunday in this example. You tell the plan which days you actually have, and it never puts two hard days back to back.

What is the longest session?

Long run with a fast finish, about 3h00 and 28 km. It is capped by share of the week, by absolute length, and by the time you say you have.

Can I use this if I train at altitude?

Yes, and you should say so when you build it. Paces and power are corrected for the difference between where you tested and where you train — in Johannesburg that is roughly 8%, or about 26 seconds a kilometre on an easy run for a 20-minute 5 km runner.

20-week marathon training plan

What the weeks are for

The 21 weeks

The biggest week, session by session

The paces

What this plan says out loud

Common questions

Other marathon plans

Goal times

South African races at this distance

Worth reading