How hard is your
New Zealand parkrun?

Section 1

Introduction and Method

Every Saturday morning, tens of thousands of New Zealanders run a free, timed 5km at one of 67 parkrun events — flat city laps, lakeside paths, river walkways, and a handful of genuine hill and quarry courses. Every finisher receives an age grade: a percentage comparing their time to a world-class standard for their age and gender, so runners of different ages can be set side by side. But that grade, by parkrun's own admission, makes no allowance for where you run. A 25-minute run up and down Halswell Quarry is a very different effort from 25 minutes along the flat at Pegasus, yet both earn the same grade for the same time.

This paper closes that gap for New Zealand. Using 497,422 valid New Zealand parkrun results from the 2025 calendar year, we derive a difficulty factor for every one of the 67 courses and combine it with the existing age and gender adjustment into a single number — the Terrain-Adjusted Grade, or TAG. A runner's TAG is comparable across every New Zealand parkrun, whatever the terrain. The full table of factors is in Section 5, and a free calculator lets any parkrunner compute their own.

A note on method

New Zealand is treated as a self-contained country. Its factors are anchored to its own fastest course — Pegasus parkrun, set to 1.000 — and built entirely from New Zealand data, exactly as the United Kingdom and Australia were each anchored to their own fastest course. The age standard, by contrast, is global: parkrun applies the same age-grading tables worldwide, so the age side needs nothing rebuilt (Section 2). The course difficulty factors were derived two completely independent ways — one from the distribution of grades across each course's whole field, the other by tracking the same runners across different courses — and only used once we had checked that the two agree.

Who runs parkrun in New Zealand

The New Zealand field is large, busy and notably balanced. Across the 67 courses there are roughly 79,900 distinct runners, averaging about six runs each, and 30% have run at two or more courses. The participation profile looks much like Australia's — a broad, social field with a substantial walking contingent — but it is the most gender-balanced of the three countries we have studied.

For context, the UK median age grade is about 52.9% on a 29:06 median finish, with only 10.4% of finishes over 40 minutes; New Zealand's lower median and heavier slow tail mirror Australia (49.8%, 31:03, 24.2%). What stands out is the gender balance — 49.4% female, ahead of Australia (47.5%) and well ahead of the UK (42.9%) — and a surprisingly strong fast end: the 99th-percentile age grade is 77.8% and 0.146% of all runs clear 85%, a slightly higher rate than either the UK or Australia despite New Zealand's far smaller field.

Section 2

Age Grading: the Same Global Standard

Age grading converts a finish time into a percentage by comparing it to a standard time — the best a runner of that age and gender might achieve:

We confirmed, by reverse-engineering the standard times implied by New Zealand's own grades, that parkrun uses the identical global table here. The recovered New Zealand base times match the same parkrun standard already established for the UK and Australia to within 0.4 seconds across the whole age range — the same open-class anchors (12:53 for men, 14:48 for women) and the same year-by-year curve. There is no separate New Zealand age standard; the age side of TAG transfers wholesale.

The female-veteran question, on a third continent

There is one well-known quirk in parkrun's tables, and New Zealand reproduces it exactly. For older women, parkrun's standard times drift progressively slower than the published ALJ standard — meaning parkrun grades older women a little more generously than the international table would. The gap is essentially zero up to age 50, then widens steadily: about 12 seconds at 50, 47 seconds at 65, and 170 seconds — nearly three minutes — by age 84. For men the gap stays negligible across the whole range.

This matters for what TAG does next. Finding the same female-veteran pattern in New Zealand — after the UK and Australia — confirms it is a global feature of parkrun's grading, not a regional quirk. Crucially, the Terrain-Adjusted Grade is built on the published ALJ standard, not parkrun's more generous version. So TAG does not inherit the inflation; it quietly corrects it. An older woman's TAG is measured against the same auditable standard as everyone else's, which is exactly why a TAG can read a little lower than the age grade parkrun shows her — the published standard is the stricter, fairer one. TAG therefore improves on parkrun's grade in two ways at once: it adopts an even-handed published age standard, and it adds the course correction parkrun makes no attempt at.

Section 3

Why Courses Differ

Age grading corrects for who you are. It says nothing about where you run. Yet the course itself is often the single biggest influence on a finish time: a flat, fast, well-surfaced lap produces quicker times than a hilly trail, and no amount of age adjustment closes that gap. The same runner, on the same morning, in the same shape, will simply post a slower time on a harder course — and under the current system, a slower grade to match.

The fix is a course speed factor: a single number, at most 1.000, describing how much a course slows a typical runner relative to the fastest course in the country. A factor of 0.90 means runners there are about 10% slower than they would be on the reference course. Multiply it through the grade and the course's influence drops out, leaving a number that reflects the runner, not the venue.

New Zealand turns out to be unusually uniform in this respect. Its courses span a narrower difficulty range than the UK's or Australia's — most are flat-to-rolling city parks, foreshores, lake circuits and river paths, with only a small number of genuine hill or quarry courses pulling the slow end down. That tight clustering is the backdrop to everything that follows.

Section 4

Two Independent Methods — and How Closely They Agree

We derived each course's factor twice, using methods that share no mathematics, and only trusted the result because the two agree.

Method 1 — grade distribution

parkrun's age grade already removes age and gender, so any systematic difference in the grade distribution between courses is the course itself. For each course we take its established runners, their best grade there, and summarise the field across nine points of the grade distribution. Comparing that profile against the best any course achieves, and taking the typical shortfall, gives the course's factor. This method uses the entire field at every venue, but it is sensitive to who turns up: a course with an unusually fast or slow regular crowd can look easier or harder than its terrain alone warrants.

Method 2 — paired runners

The second method tracks the same runners across different courses. If a runner is typically 8% slower at course B than at course A, that 8% is the courses talking, not the runner — their fitness cancels out. Pooling every such comparison across all the runners who have run two or more New Zealand courses, and solving for the set of course factors that best fits them all at once, gives a second, independent estimate. Each runner is their own control, so this method is immune to the field-composition effect that can sway Method 1.

The two methods agree more closely than anywhere we have looked

Across all 67 courses the two estimates correlate at r = 0.776, and — more tellingly — they differ by just 1.8% on average. That absolute agreement is tighter than Australia's (mean difference 5.1%) and tighter even than the UK's (3.6%), despite New Zealand's smaller field. Two methods built on entirely different evidence landing within 1.8% of each other across every course is strong assurance that the factors measure genuine terrain difficulty rather than an artefact of either method.

Where they part — and why we still blend evenly

The disagreements are small and read sensibly. The largest is Wanaka, where the grade-distribution method reads about 5% faster than the paired method — a Central Otago resort course whose visiting field flatters the grade-distribution view. A handful of smaller regional courses (Whanganui Riverbank, Ōroua River Walkway, Foster) go the other way, rated a little faster by the paired method once the local field's pace is controlled for. But none of these gaps exceeds about 5%, a fraction of the swings seen in Australia, where rugged outback and bush-trail courses pushed the two methods 15–17% apart and forced a careful investigation. Here there is nothing of that scale to arbitrate. We take the straight average of the two methods — which lets each offset the other's known weakness — and re-anchor so the fastest course reads 1.000.

Section 5

Course Speed Factors — All 67 New Zealand parkruns

The blended factors run from 1.000 down to 0.814, with a median of 0.967. That range — under 19 percentage points top to bottom — is the tightest of the three countries (Australia spans to 0.69, the UK to 0.74). New Zealand simply has fewer punishing courses: the bulk cluster between 0.94 and 1.00, and only a short tail of hill, crater and quarry courses sits below 0.92.

67 courses. Factor of 1.000 = Pegasus (reference). Blended from grade-distribution and paired-runner methods.

Section 6

The Terrain-Adjusted Grade

Combining the age and gender correction with the course factor gives a single number — the Terrain-Adjusted Grade — that accounts for who you are and where you run:

Because the course factor sits in the denominator, a hard course lifts the grade to compensate: run 25:00 at Halswell Quarry (0.814) and your TAG treats it almost as generously as a much faster time on the flat, because the course was working against you. A runner's TAG is the same measure of effort whether they ran a lake circuit in Taupō or a quarry loop in Christchurch.

TAG also works as a predictor. Given a time at one course, the expected time at another follows from the ratio of their factors:

Section 7

Notes, Limitations and Next Steps

The factor describes the whole performance environment of a course, not just its gradient: surface, exposure, the number of turns, and the typical start conditions are all absorbed into one number. That is a feature — it is what a runner actually faces on a Saturday — but it means the factor should be read as "how this course runs", not purely "how steep it is".

Limitations

• Small courses. A few courses have thinner data and slightly less certain factors; the grade-distribution method in particular leans on a course's regular field, which at small venues may not represent the terrain alone. The paired method and the even blend guard against this, but the factors at the smallest courses should be treated as more provisional.
• Female-veteran age factors. TAG uses the published ALJ standard, which removes parkrun's older-women generosity — but the ALJ female factors at the oldest ages are themselves built on sparse records and remain the highest-priority area for refinement.
• Course stability. Factors reflect each course's 2025 configuration; a re-routed or re-surfaced course would need recalculating.

What we are building

The full set of factors and a free calculator — compute your TAG, compare your times across the New Zealand courses, and predict your expected time at any venue — are at parkrun-calculator-anz.openair.tools, which now covers Australia and New Zealand. TAG also underpins the cross-distance race predictor at skamper.openair.tools, which estimates times from a single recent result across distances from parkrun to ultramarathon.