Ultra Marathon Distance: 50km, 100km and 100-Mile Standards in New Zealand

An ultra marathon distance is any footrace longer than the standard marathon distance of 42.195 km (26.2 miles). In practice the sport has settled on a handful of recognised standards — the 50 km, the 100 km and the 100-mile “miler” (161 km) — alongside non-standard trail classics and time-based formats where the distance is whatever you can cover. This guide explains exactly how far each ultra distance is, how long it typically takes, and what changes physically and logistically as you step up, using verified New Zealand events from the volcanic trails of Rotorua to the alpine ridgelines of Fiordland as reference points.

What Counts as an Ultra Marathon Distance?

An ultra marathon is officially defined as any race longer than 42.195 km, so technically a 43 km event already qualifies. The sport recognises a small set of “standard” distances: 50 km, 50 miles (80 km), 100 km and 100 miles (161 km). The International Association of Ultrarunners (IAU) and World Athletics ratify records at 50 km and 100 km, and the IAU also recognises timed formats such as the 24-hour race. Everything else — a 60 km mountain loop, an 85 km back-country traverse — is dictated by the terrain rather than a round number.

The practical point is that an ultra is measured in hours and vertical metres as much as in kilometres. A flat 50 km on a lakeside trail and a 50 km with 3,000 m of climbing are the same distance but a completely different day out. That is why experienced runners talk about “racing the terrain” rather than racing the clock, and why time limits (cut-offs) matter as much as pace targets. For a broader overview of the scene, our guide to the ultramarathon in New Zealand covers events, training and how to start.

The 50km Ultra: The Gateway Distance

The 50 km is the most common entry point to ultra running because it is only about 7.8 km longer than a marathon. New Zealand events such as the Tarawera T50 (part of the Tarawera Ultra-Trail by UTMB in Rotorua) and the 50 km option at the Taupō Ultramarathon are designed to be achievable for a fit marathoner while introducing trail-specific demands: single-track, forestry roads, stream crossings and real climbing.

The training base is similar to a marathon, but the emphasis shifts from speed to “time on feet” and trail strength. Most first-timers walk the steep climbs, spend a minute or two at each aid station, and finish 60–90 minutes slower than they would run a road marathon — which is normal, not a failure.

Stepping Up From 42.195 km to 50 km

The extra distance feels larger than 7.8 km because it arrives on tired legs over rougher ground. Practise “power hiking” (fast, purposeful walking up hills) so that climbs do not spike your heart rate, add one trail long run each week, and get comfortable eating while moving. If your target race has significant elevation, treat the climbing — not the distance — as the thing you are training for.

The 100km Ultra: The Metric-Century Benchmark

The 100 km is the benchmark for seasoned endurance runners and the shortest distance that counts as a Western States 100 qualifier (which requires a 100 km trail race with at least 100 finishers). It is also where UTMB’s “Running Stones” qualification system comes into play, and the Taupō 100 km is a listed Western States qualifier. Expect roughly 10 to 17 hours on your feet depending on terrain, which almost always means running from daylight into darkness.

At this distance the race becomes a logistics and fuelling problem as much as a fitness test. Thousands of metres of vertical gain tax your quads and balance, and small nutrition errors compound over the hours. The Tarawera T102 in Rotorua is New Zealand’s best-known 100 km, and the Tarawera Ultra results show how widely finish times spread across the field.

Fuelling the 100km

Running for 10 to 17 hours needs a rehearsed fuelling plan. Most 100 km runners aim for 200–350 calories and 300–600 mg of sodium per hour, practised in training so the gut can absorb food under effort. As blood diverts to the legs, digestion slows, so many runners switch from gels to “real food” — salted potatoes, sandwiches, flat cola — in the later stages.

The 100-Mile Miler: New Zealand’s Longest Single-Stage Races

The 100-mile (161 km) distance, known as the “miler,” is the longest common single-stage ultra. In New Zealand the headline events are the Tarawera TMiler (about 163 km) and the Northburn 100 near Cromwell, which packs roughly 9,460 m of climbing into its 161 km course and is regarded as the country’s original and toughest 100-miler. Finishing a miler usually means running through at least one full night, managing sleep deprivation, and keeping electrolytes and blood sugar stable for 24 to 40 hours.

At this distance “running” becomes sustained forward motion: a mix of jogging the runnable sections, hiking the climbs and simply refusing to stop. Self-sufficiency and mandatory safety gear are non-negotiable because much of the course is deep in remote alpine or volcanic country.

The Mental Side of 161 km

Low points are guaranteed over 100 miles. The standard coping tool is “chunking” — breaking the race into aid-station-to-aid-station segments so you only ever focus on the next 10–20 km. Eating and drinking on schedule, changing socks, and getting through the pre-dawn hours usually turns a crisis around; most “I’m done” moments pass within an hour.

How the Ultra Distances Compare

The jump from 50 km to 100 km to 100 miles is not linear: time on feet, calories burned and gear requirements all climb sharply. The table below summarises typical demands for a mid-pack runner on New Zealand trails — use it to set realistic expectations, remembering that a technical course can take far longer than a flat one of the same length.

Non-Standard Distances: Kepler, Old Ghost and Molesworth

Some of New Zealand’s most prestigious ultras ignore round numbers entirely because their distance is set by the trail itself. The Kepler Challenge is a 60 km mountain run on the Kepler Track in Fiordland with about 2,080 m of climbing, held every December since 1988. The Old Ghost Ultra covers 85 km of remote West Coast wilderness along the Old Ghost Road from Seddonville to Lyell, with roughly 2,700 m of ascent and no road crossings from start to finish.

• Kepler Challenge (60 km): point-to-loop mountain run, ~2,080 m vertical, 12-hour limit, Fiordland National Park.
• Old Ghost Ultra (85 km): a remote traverse of a historic gold-mining and mountain-bike track on the West Coast.
• The Molesworth Run (84 km): a high-country off-road ultra from the Molesworth Cob Cottage to Hanmer Springs through New Zealand’s largest high-country station.
• WUU2K (~62 km): the Wellington Urban Ultra, a technical ridge-run around the capital with shorter 21 km and 43 km options.

Technicality Versus Distance

An 85 km technical trail in the South Island can take longer to finish than a flat 100 km road ultra, so distance alone is a poor measure of difficulty. When choosing an event, look at vertical gain per kilometre and the cut-off times, not just the headline number — a “shorter” race with 3,000 m of climbing may be the harder day.

Backyard Ultras and Time-Based Formats

A fast-growing corner of the sport abandons a fixed distance altogether. In a Backyard Ultra, runners complete a 6.706 km loop (the “yard”) at the start of every hour; anyone who fails to finish a loop in the hour, or chooses to stop, is out. The race continues until one runner completes a loop alone — the only official finisher, while everyone else is recorded as a DNF (Did Not Finish). The loop length is deliberate: 24 loops equal exactly 100 miles (160.9 km) in 24 hours, so the format is theoretically endless, and top athletes now run for multiple days. You can read more about the wider sport on Wikipedia.

Timed races work on the same “distance is the outcome” logic. In a 6-hour, 12-hour or 24-hour event, runners circle a short measured loop and your result is simply the total distance covered before the clock runs out — a format that rewards steady pacing and mental stamina over raw speed.

The Maths of the Yard

The 6.706 km loop equals 4.167 miles, and 4.167 × 24 = 100 miles. That design lets a runner reach the miler milestone after a full day of racing, and it makes every backyard event directly comparable: success is measured in “yards” completed rather than kilometres per hour.

Pacing Across Different Ultra Distances

Pacing an ultra is about energy preservation, not holding a fixed speed. For a 50 km you can run a steady aerobic effort, but over 100 km or 100 miles the priority is avoiding the “blow-up” that follows going out too hard. Walking the uphills is a tactical choice used by elites, not a sign of weakness, because it keeps heart rate and glycogen use in check.

• Start too easy: aim to reach halfway feeling like you have barely begun.
• Hike the climbs: if you cannot see the top of a hill, you should probably be power hiking it.
• Be efficient at aid stations: know what you need before you arrive so you keep moving and hold core temperature.
• Use effort, not pace: heart-rate zones or perceived effort track your real cost far better than minutes-per-kilometre on varied terrain.

Mandatory Gear for New Zealand Trails

As the distance grows, so does the time you spend far from help, and most New Zealand ultras enforce a mandatory gear list checked at registration and sometimes at random on course. Alpine weather in the South Island or geothermal humidity around Rotorua can turn dangerous within minutes even in summer, so gear is a safety requirement rather than a suggestion — turn up without it and you will not be allowed to start. A well-fitted hydration pack is what carries most of this kit comfortably.

• Waterproof jacket: seam-sealed, with a meaningful waterproof rating for wind and rain protection.
• Thermal layer: merino or polypropylene (never cotton) to manage the risk of hypothermia.
• Survival blanket and whistle: basic emergency shelter and a way to signal for help.
• Headlamp plus spare batteries: essential for the night sections of 100 km and 100-mile races.
• First-aid basics and a charged phone: for immediate injury care and emergency contact.

Fuelling and Hydration Over Long Distances

Ultra fuelling is often called “an eating contest with some running involved,” because the limiting factor is frequently your stomach, not your legs. As the hours pass, digestion becomes harder, so the goal is to train your gut in advance to absorb a steady stream of calories and fluid. Practise your exact race-day plan on long training runs rather than trying anything new on the day.

• Fluid: roughly 400–800 ml per hour, adjusted for heat and humidity.
• Sodium: about 300–600 mg per hour to reduce cramping and hyponatraemia risk.
• Calories: 200–350 per hour, mixing fast gels with solid food for satiety on easier sections.
• Gut training: rehearse fuelling every long run so race day holds no surprises.

Common Mistakes When Stepping Up in Distance

The most common ultra mistakes have little to do with fitness. New ultra runners routinely undo months of training in the first two hours, and the errors repeat across every distance and event.

• Starting too fast: the single biggest cause of blow-ups; the early kilometres should feel almost too easy.
• Under-fuelling early: waiting until you feel hungry or flat is too late — eat and drink from the first hour.
• Training distance but not vertical: if your race climbs 3,000 m, flat long runs leave your quads unprepared for the descents.
• New gear on race day: untested shoes, packs or nutrition cause blisters and stomach trouble; nothing should be new.
• Ignoring the cut-offs: banking too little time early, then missing an aid-station cut-off, ends more races than injury does.
• Treating gear checks as optional: missing mandatory items means no start, regardless of fitness.

How to Choose Your First Ultra Distance

Choose your first ultra by matching the distance and terrain to your current training, not your ambition. A fit marathoner is usually ready for a runnable 50 km within a few months; the 100 km and 100-mile distances reward a year or more of consistent trail volume and at least one shorter ultra behind you. The best first ultra is one where you respect the cut-offs and finish healthy, rather than the longest number you can enter.

• New to trails, strong road base: a flatter 50 km such as a lakeside or forest course.
• Experienced marathoner, some trail time: a hilly 50 km or a 60–85 km classic like the Kepler Challenge.
• Several ultras finished, high weekly volume: a 100 km, with 100-mile events as a multi-year goal.
• Curious about your limits: a timed or backyard event, where you set the distance and can stop with dignity.

Whatever you target, interest in long-distance racing keeps rising, and if you are curious about how fields and finish rates actually play out, our look at the odds of winning an ultramarathon puts the numbers in perspective.

Safety note: Ultra-distance running is physically demanding and carries real risks, including hypothermia, heat illness, hyponatraemia and overuse injury. This article is general information, not medical or coaching advice. Consult a doctor before starting ultra training, follow each event’s mandatory gear and cut-off rules, and never enter remote back-country terrain beyond your experience.

Frequently Asked Questions

How far is an ultra marathon exactly?

An ultra marathon is any footrace longer than the marathon distance of 42.195 km. The recognised standard distances are 50 km, 50 miles (80 km), 100 km and 100 miles (161 km), with many trail events falling at non-standard lengths set by the course.

What is the shortest ultra marathon distance?

Any race over 42.195 km qualifies as an ultra, so the shortest possible ultra is just beyond a marathon. In practice, 50 km is treated as the standard entry-level ultra distance and is where most road runners make the step up.

What is a “miler” in ultra running?

A miler is a 100-mile race, which equals 160.934 km. It is the longest common single-stage ultra distance and usually involves running through at least one full night, with finish times ranging from around 24 to 40 hours.

Is it normal to walk during an ultra marathon?

Yes. Power hiking the climbs is a standard tactic used by almost everyone, including elite runners, to control heart rate and preserve energy. On steep or technical terrain it is often faster and far more efficient than trying to run.

Do I need trail shoes for a 100km ultra?

For almost all New Zealand 100 km events, yes. Trail shoes provide the grip, rock protection and stability that road shoes lack on muddy, rooty and rocky terrain, reducing the risk of slips and foot bruising over a long day on the trails.