How to Rate Hiking Difficulty
Six factors determine real trail difficulty: distance (longer = more sustained effort), total elevation gain (total climbing in metres or feet), elevation gain rate (m/km, steepness is often more important than total gain), terrain type (paved path vs rocky scramble), exposure (cliffs, ridgelines, weather risk), and weather (heat, cold, rain, snow). This calculator combines distance and elevation into a single Shenandoah score, then maps onto the universal Easy–Expert scale. Estimate your hiking time on the rated trail with our Naismith's Rule calculator.
Popular Hiking Rating Systems
Different regions use different scales. The Swiss SAC scale (T1–T6) is the European standard, focused on terrain technicality rather than effort. The Yosemite Decimal System (YDS Class 1–5) ranks technical difficulty from walking (Class 1) to climbing (Class 5). The Shenandoah National Park formula used by this calculator combines distance and elevation into one number. The US NPS uses a subjective Easy/Moderate/Strenuous/Very Strenuous rating that varies by park. This calculator provides a universal rating that works internationally. Calculate calories burned on your rated trail with our hiking calorie calculator, and check your pack weight before a hard hike with our backpack weight calculator.
Petzoldt Energy Mile System
The Petzoldt Energy Mile system was developed by Paul Petzoldt, founder of the National Outdoor Leadership School (NOLS) and the Wilderness Education Association (WEA). It converts elevation gain into equivalent flat-distance miles to produce a single difficulty number.
The formula:
Energy Miles = distance (miles) + elevation gain (feet) ÷ 500
The concept: every 500 feet (152m) of elevation gain requires the same effort as walking one additional flat mile. A 5-mile hike with 2000 ft of elevation gain = 5 + 4 = 9 Energy Miles, equivalent in effort to a 9-mile flat walk.
Why it's useful: Energy Miles are intuitive, most hikers know how long it takes them to walk a flat mile (15–20 minutes). Multiply Energy Miles by your flat-mile pace to estimate total time.
| Energy Miles | Petzoldt Rating |
|---|
| < 5 | 🟢 Easy |
| 5–8 | 🟡 Moderate |
| 8–12 | 🟠 Hard |
| 12–16 | 🔴 Very Hard |
| 16+ | 🟣 Extreme |
Shenandoah vs Petzoldt, Which Rating System Is Better?
Both systems combine distance and elevation gain into a single difficulty score, but they work differently:
Shenandoah uses a square root function, this means very long or very steep hikes don't produce disproportionately extreme scores. Good for comparing hikes across a wide range of difficulties.
Petzoldt uses linear addition, every 500 ft of gain adds exactly 1 Energy Mile, regardless of distance. Simpler and more intuitive, but can produce very high numbers for alpine routes with massive elevation gain.
Recommendation: Use Shenandoah for trail ratings and comparison. Use Petzoldt for time estimation (Energy Miles × your pace = estimated time). The calculator above shows both.
Difficulty Ratings Compared, Example Hikes
See how the two systems rate the same hike, and where they disagree:
Notice how the two systems sometimes disagree, the "short but very steep" hike is Challenging on Shenandoah but only Moderate on Petzoldt. This is because Shenandoah's square root function amplifies steep hikes more than Petzoldt's linear formula. Both are valid perspectives on difficulty.
Where each scale fails
Both formulas have a blind spot, and they are opposite ones. That is the reason this page runs two scales instead of picking a favourite, and the reason the rating at the top follows whichever of them is harsher.
Shenandoah goes blind on flat ground. Its formula multiplies distance by elevation, so when the elevation is zero the product is zero and the square root of zero is zero however far the route runs. Enter 30 km with no climbing and it returns a score of 0, the bottom of its Easy band, for what is a six to eight hour walk. Petzoldt puts the same route at 18.6 energy miles, which is its second highest band. This is a property of the original formula rather than of our arithmetic, and the page names it in the result rather than quietly passing it on.
Petzoldt flattens very steep, very short routes. It adds a fixed penalty per 500 feet of climb regardless of how that climb is packed into the distance. Two kilometres with 3000 metres of ascent comes out at 20.9 energy miles, more than the 18.6 of a flat 30 km day. That is defensible, since climbing three vertical kilometres is a serious undertaking, but it is worth knowing that the number says nothing about the terrain that ascent is on. Shenandoah rates the same route Hard at 156, and neither figure tells you whether it is a path or a scramble.
Neither scale accounts for terrain underfoot, weather, altitude, pack weight or how well you know the route. They are both functions of two numbers, and two numbers is not a day on the hill.
Where these numbers come from
The two formulas are published and are reproduced here unchanged. Shenandoah National Park publishes the square root model, and the Petzoldt energy mile comes from Paul Petzoldt by way of NOLS and the Wilderness Education Association.
The band edges are a different matter and we could not establish them from either source. Where Easy stops and Moderate begins, and the four bands the Shenandoah score is cut into, are this site's working thresholds, and so is the mapping of Petzoldt's five bands onto the same ladder to decide which rating is harsher. The formulas are theirs; the labels around them are ours.
Frequently asked questions
What is Petzoldt Energy Miles?
Petzoldt Energy Miles is a hiking difficulty system developed by Paul Petzoldt (founder of NOLS). It converts elevation gain into equivalent flat miles: every 500 feet (152m) of gain = 1 additional Energy Mile. A 5-mile hike with 2000 ft gain = 9 Energy Miles. Multiply by your flat-mile pace to estimate hiking time.
Which hiking difficulty system should I use, Shenandoah or Petzoldt?
Use Shenandoah for trail ratings and comparing hikes (it handles extreme routes better due to the square root function). Use Petzoldt for time estimation, Energy Miles × your per-mile pace gives a quick time estimate. The calculator above shows both systems side by side.
What is a hard hike in terms of elevation gain?
A hike with 800–1500m (2600–5000 ft) of total elevation gain is generally considered hard. Above 1500m gain is expert-level. However, difficulty also depends on distance, 1000m gain over 5km is much harder than 1000m over 20km.
How do you calculate hiking difficulty?
Hiking difficulty is determined by combining distance, total elevation gain, elevation gain rate (metres per kilometre), and terrain type. The most important factor is elevation gain rate, a steep 5km hike can be harder than a flat 20km walk.
How is hiking difficulty calculated?
This calculator uses the Shenandoah National Park formula: Difficulty = √(elevation gain in feet × 2 × distance in miles). The formula was developed to give a single number reflecting both length and steepness. A score below 50 is Easy, 50–100 is Moderate, 100–150 is Challenging, above 150 is Hard. It was designed for trail management but is widely used by hikers to compare route difficulty.
What is an easy hiking trail?
An Easy trail scores below 50 on the Shenandoah difficulty scale. This corresponds roughly to routes under 8km with less than 200m of elevation gain, or longer flat routes with minimal climbing. Easy trails are suitable for beginners, families with children, and casual walkers with no specific fitness preparation. Most well-known tourist trails and lakeside walks fall in this category.
Is a 10km hike with 500m elevation hard?
A 10km hike with 500m elevation gain scores approximately 143 on the Shenandoah scale: Challenging. It requires good fitness and proper footwear. Allow 3.5–4 hours including breaks. Bring at least 1.5–2 litres of water, a packed lunch, appropriate footwear, and navigation. This is a solid day hike suitable for regularly active hikers.
What are energy miles in hiking?
Energy miles (developed by Paul Petzoldt for NOLS) express the total effort of a hike as an equivalent flat distance. The formula adds 1 energy mile for every 500 feet (152m) of elevation gain. A 6-mile hike with 2,000 feet (610m) of gain equals 10 energy miles, the equivalent effort of a 10-mile flat walk. Energy miles are useful for comparing hikes of different distances and elevations.
How does trail difficulty affect preparation?
Easy trails (score below 50) need minimal preparation beyond water and appropriate footwear. Moderate (50–100) requires a full day pack with food, extra water, navigation, and a rain layer. Challenging (100–150) requires good fitness, hiking boots, trekking poles, emergency kit, and ideally some experience. Hard (above 150) demands significant fitness, full mountain safety equipment, and experience on exposed terrain.
What difficulty level should a beginner hike?
Beginners should start with Easy trails (score below 50) to build fitness and confidence. After 4–6 Easy hikes, most people can progress to Moderate (50–100). Challenging trails (100–150) require a foundation of at least 10–15 hikes including some with significant elevation. Hard trails are for experienced hikers with established fitness and navigation skills.
How does the Shenandoah formula compare to other difficulty systems?
The Shenandoah formula combines both distance and elevation into one number, which is more useful than systems that rate difficulty on subjective scales (easy/moderate/hard) without numerical values. Other park systems (Yosemite, Swiss SAC) use different criteria including trail conditions and technical difficulty. The Shenandoah formula is primarily useful for comparing similar trail types; it does not account for path quality, exposure, or navigation difficulty.
Why does elevation gain matter more than elevation loss in difficulty?
Climbing requires more sustained muscular effort and cardiovascular work than descending. The difficulty formula only accounts for elevation gain (D+) because ascent is the primary physical challenge. Steep descents add difficulty through knee and ankle stress, but this is harder to quantify. For routes with very steep descents, consider the score an underestimate and add extra time for careful downhill walking.