Multi-leg time estimator — Naismith's Rule + Langmuir descent corrections + Tranter fitness adjustment
Tranter fitness: time to climb 300 m (1,000 ft) over 800 m (½ mile) of ground. Drop one level for heavy pack, rough terrain, or bad weather. Slowest group member governs.
Add one row per leg (e.g. Start → Summit, Summit → Bealach, Bealach → Finish). Descent angle: flat/negligible = no Langmuir adjustment; 5–12° = gentle; >12° = steep.
Add at least one leg with a distance to see results.
Use Ordnance Survey (OS) Maps (osmaps.ordnancesurvey.co.uk) or Komoot / Strava Route Builder to measure each leg. OS 1:25,000 (Explorer) and 1:50,000 (Landranger) maps show contours at 10 m and 20 m intervals respectively. For accurate ascent, use GPX data — visual estimates of ascent are typically wrong by 20–30%.
Langmuir descent correction (per leg): subtract 10 min per 300 m of gentle descent (5–12°); add 10 min per 300 m of steep descent (>12°). No adjustment for flat or negligible slopes. Source: Langmuir, Mountaincraft and Leadership, 1984.
Tranter's fitness multiplier: your measured time to climb 300 m over 800 m of ground is used to place you on Tranter's published table, which adjusts the Naismith total. Very fit walkers (15 min) can complete Naismith's route in roughly half the time; unfit walkers or those in adverse conditions may take substantially longer. Source: Tranter, The Munroist's Companion, referenced in Langmuir (1984).
The terrain modifier per leg adds a small buffer: good path (no change), rough or boggy ground (×1.15), and boulder/scree/snow (×1.30). These are applied after Langmuir's descent correction and before Tranter's multiplier. Adjust your Tranter fitness level down one tier for severe weather or a pack heavier than 15 kg.
Route cards are used by Mountain Leader trainees, Duke of Edinburgh expedition supervisors, school and youth group leaders, and experienced hillwalkers heading into remote terrain. They serve two purposes: personal planning (realistic finish time, turnaround decisions) and safety (a copy left with a contact who can alert mountain rescue if you don't check in by your planned latest return time).
Mountain Rescue teams in Scotland and England/Wales recommend leaving a route card with a reliable contact before any serious hill day. The route card should include start and finish points, expected return time, and emergency contacts. This calculator generates all of those automatically from your inputs.
⚠ This calculator provides planning estimates only. Naismith's Rule and its corrections are rules of thumb with real-world variance of ±20–30%. Conditions change rapidly in mountain environments. Always carry a map and compass, check weather forecasts, and ensure someone reliable holds your route card and knows when to raise an alarm. This tool does not constitute professional mountain safety advice.
Naismith's Rule, devised by Scottish mountaineer William W. Naismith in 1892, estimates hill walk time as: 1 hour per 5 km of horizontal distance, plus 1 hour per 600 m of ascent. It assumes a reasonably fit walker on good terrain and should be treated as a minimum time — real-world conditions nearly always add to it.
Eric Langmuir (Mountaincraft and Leadership, 1984) extended Naismith's Rule to account for descent steepness. On gentle descents (5–12°), walkers move faster, so subtract 10 minutes per 300 m of descent. On steep descents (>12°), progress is slower and more careful, so add 10 minutes per 300 m. Very shallow descent has no significant effect on time.
Tranter's corrections, published in The Munroist's Companion, adjust Naismith's base time for individual fitness. Fitness is benchmarked by how long it takes to climb 300 m over 800 m of ground. A very fit walker (15 min) can roughly halve Naismith's time; a very unfit walker (50 min) may need nearly double. For adverse conditions, heavy packs, or difficult terrain, drop one fitness tier.
A route card is a planning document used in UK hillwalking and mountain leadership training. It breaks a route into legs — typically between waypoints or features — and records each leg's distance, ascent, descent, bearing, estimated time, and any notes. A copy is left with a safety contact who knows when to call mountain rescue if you don't check in. Route cards are a core skill in UK Mountain Leader and Duke of Edinburgh programmes.
It is a well-tested rule of thumb, typically accurate to ±20–30% for fit walkers on good terrain. It underestimates time on rough or boggy ground, in bad weather, for groups with mixed ability, and for heavy loads. Always add buffer time — especially in winter, remote locations, or when the calculated finish time is close to sunset.
Ordnance Survey maps use the metric grid, so km and metres are standard for UK hillwalking route planning. This calculator supports both — toggle between km/m and miles/ft using the unit selector, and all inputs, headers, and results update together.
A multi-leg route card more accurately reflects real hill walks, which typically have distinct sections: an approach, a ridge traverse, a summit push, and a descent. Each leg may have different ascent, descent steepness, and terrain, so Langmuir's correction applies differently per section. Summing per-leg adjusted times gives a more accurate total than applying corrections to averaged whole-route figures.