Calcz
Guide 03 / Six chapters · one race plan

From sign-up
to the start line.

Pick your distance, or a specific race, then scroll. We work out where your fitness stands, a realistic goal, a periodized week-by-week plan, your race-day pacing, and how to fuel it. Every chapter writes a line on your race plan. No ads, no accounts, nothing stored.

Scroll. It starts with your race
01 / The race

It starts with a distance to chase.

Training for a specific race? Pick the distance and the day. No date in mind? Train for a distance with a best-practice block. Your goal, plan, pacing and fuel all build around this.

Mode
Distance
8 wk24 wk
Half block12 week blockA general 12 week block toward your Half. No race date needed; drag to fit your calendar.
02 / Where you stand

Find out how fit you already are.

Before you chase a goal, see where you start. Enter a recent all-out result, a parkrun, a time trial, or a recent race. Age grading scores it against the world-class standard for your age and sex, so it is fair whatever your decade.

Recent result distance
Finish time
:
:
hours : minutes : seconds
Sex (age grading)
Age-graded score52.2%That is a recreational score against the world-class standard for your age. We will seed your plan at a novice starting load a few chapters down; adjust it there if you know your own mileage.

Your score is your time as a percentage of the world best for your age and sex, so it is fair whatever your decade; higher is fitter. A recreational score means roughly a solid everyday runner. That time is faster than about 91% of race finishers.

RunRepeat: State of Running (global race finishers)Top 9% · Competitive
parkrun UK: Saturday 5K (all finishers)Top 31% · Serious

Percentile spreads are anchored on published average times and modeled at the edges. Treat the band as the signal.

03 / The goal

A target time you can actually hit.

Your recent result sets what you can run today. From there we forecast a realistic target for race day using your training block and Daniels' VDOT model, then let you set your own. Pacing and fuel below follow the target.

Target time (Half)1:49:32About 5:12 /km the whole way. You can run about 1:55:00 today; this target adds a realistic training improvement over your 12-week block. It implies a 53% age-graded effort.
Adjust your target
:
:
hours : minutes : seconds
The science: your fitness
38.3VDOT+2.340.6

A realistic VDOT gain over your block lifts your whole range, not just race day. Target sits at 53% age grade (recreational).

5K
0:23:49
10K
0:49:25
Half
1:49:35
Full
3:47:01

VDOT is a single fitness number derived from a race result (Daniels and Gilbert); higher is fitter. It sets your training paces and predicts your times across distances. A training block raises VDOT at a realistic rate (roughly one point every 4 to 6 weeks, faster for newer runners, slower for advanced), which we apply to your current-equivalent time. The baseline equivalent uses the Riegel formula, so it matches the standalone Race Time Predictor.

Sources: Jack Daniels, Daniels' Running Formula; gain rates per coaching consensus (see the running benchmarks data file). Learn more

Forecast uses the Daniels VDOT model applied to your current-equivalent time. Marathon targets run optimistic without a long-run base.

04 / The plan

A plan that builds, then backs off.

This is periodization: mileage rises gradually, steps back every fourth week so you absorb it, peaks, then tapers. Most running stays easy, with one quality session once you are deep in the build. We seed it from your fitness; adjust the dials to your life.

5.0 km100.0 km
Runs per week
Taper length

Your taper: 2 weeks. 3 weeks suits the marathon or high mileage, 2 weeks shorter races; cut volume about 40 to 60 percent while holding intensity (Mujika and Padilla).

Your plan12 weeksPeaking at 47.5 km a week, with a longest run near 19.0 km. 2 cutback weeks and a taper before race day.
123456789101112
Deeper = long run, lighter = weekly volumeRace distanceCutbackBar colour = phase (band above)

Tap any week above to open its Monday-to-Sunday training week.

Week 10Peak47.5 km · long 19.0 km

Drag a session to another day, or use its day menu.

  • Mon
    Easy 10.3 km6:03 /km to 6:57 /km
  • Tue
    Intervals 7.8 km4:50 /km
  • WedRest
  • Thu
    Easy 10.3 km6:03 /km to 6:57 /km
  • FriRest
  • Sat
    Long 19.0 km6:03 /km to 6:57 /km
  • SunRest
05 / Race day

Pace it so you finish strong, not sorry.

The most common race-day mistake is starting too fast. A negative split, easing out and speeding up, tends to produce better times and a better last few miles. Pick a strategy and see what each segment should read on your watch.

Pacing strategy
Average pace (km)5:12 /kmHold one pace the whole way. Simple and reliable for most runners.
First km (#1)5:12 /km
Middle km (#11)5:12 /km
Last km (#21)5:12 /km
06 / Fuel

Feed the engine before it stalls.

Anything past about 75 minutes drains your glycogen, and an empty tank is the wall. We scale carbohydrate to your goal time and experience. Practice it on long runs, never try something new on race day.

Race-day carbohydrate40 g/hrOver a roughly 110-minute race that is about 73 g of carbs in total, plus around 600 ml of fluid an hour. Use gels, drinks, or chews you have rehearsed.

Guidance follows ACSM and ISSN ranges: 30 to 60 g of carbs an hour, up to about 90 g for trained guts using multiple carb sources.

Your race plan

Everything above, in one place.

Your goal, your plan, your pacing and your fuel for Half Marathon day, all on one race plan. The link carries your numbers, and nothing is stored on a server.

Calcz · race plan5 Jul 2026
Race··
Where you stand··
Target time··
about 1:55:00 today
Plan··
Race pace··
Fuel··

Go deeper on any step

Each chapter above has a full calculator behind it, with more options and a proper write-up of how the numbers work.

How this guide works

Every chapter shares one race. You pick the distance and date, then each step (where your fitness stands, a realistic goal time, a periodized training plan, your race-day pacing and your fuel) writes a line on a running race plan you can copy as a link. Nothing is stored and no account is needed.

How long do I need to train for a race?

A common guideline is around 8 to 12 weeks for a 5K or 10K from a reasonable base, 12 to 16 weeks for a half marathon, and 16 to 20 weeks for a marathon. The guide sets the length from your race date and builds the plan backward, with a base, build and peak phase and a taper before race day.

What time should I aim for?

A realistic goal comes from a recent result, not a wish. The guide uses the Riegel formula to scale a recent race or time trial to your race distance, which is the standard way to predict times across distances. Marathon predictions assume you put in the long-run endurance work, so treat them as a ceiling to train toward.

How much should I increase my mileage each week?

A widely used rule of thumb is roughly 10 percent a week, with a cutback every third or fourth week so your body absorbs the work. Most of your running should be easy, with about one harder quality session a week once you are into the build phase. The guide applies this 80/20 split and caps the long run at around a third of weekly volume.

Should I run even or negative splits?

For most runners, a negative split, starting a touch conservative and finishing faster, produces a better time and a better last few miles than going out hard. The pacing chapter turns your goal time into the exact per-kilometer or per-mile splits to run for an even, negative or positive strategy.

Do I need to take gels during a race?

For efforts under about 75 minutes, water is usually enough. Beyond that, taking on carbohydrate matters: common guidance is 30 to 60 grams an hour, and up to about 90 grams for trained runners using multiple carbohydrate sources. Always practice your fueling on long runs rather than trying something new on race day.

Figures are estimates for guidance only. Predictions use the Riegel formula; age grading uses World Masters Athletics / USATF road tables; population percentiles are anchored on published average times (RunRepeat, parkrun) with modeled spreads; training and fueling guidance follow standard periodization and ACSM / ISSN ranges. This is general information, not coaching or medical advice.