How 21 km Becomes 28,378 Steps
Divide the distance by the average adult stride to get steps: 21,000 m ÷ 0.74 m ≈ 28,378 steps. In miles that's 13.05.
Height matters: at 155 cm you'd need about 32,726 steps, at 190 cm about 26,697 steps for the same 21 km. A taller walker takes fewer steps for the same distance.
Time to cover 21 km: 4h 12min moderate, 3h 14min brisk, 5h 15min slow.
How long does 21 km take on foot?
Moderate 5 km/h: 4h 12min. Brisk 6.5 km/h: 3h 14min. Slow 4 km/h: 5h 15min. Race-walk 8 km/h: 2h 38min.
Calories burned walking 21 km
A 70 kg adult burns ~1080 kcal at moderate pace across 21 km. The 55–100 kg range spans 849–1544 kcal. Brisk 6.5 km/h raises a 70 kg walker to ~1187 kcal.
Steps by height
Because stride scales with leg length, step counts for the same 21 km vary widely. The table below shows exact step counts by height using the standard height×0.414 stride estimate.
Is walking 21 km worthwhile?
Approaches long-hike or event-day mileage — recover with hydration and light stretching. A brisk pace burns ~40% more calories per minute than a slow stroll — for the same distance.
Steps in 21 km by Height
| Height | Avg stride | Steps |
|---|---|---|
| 155 cm (5'1") | 0.64 m | 32,726 steps |
| 165 cm (5'5") | 0.68 m | 30,742 steps |
| 170 cm (5'7") | 0.70 m | 29,838 steps |
| 175 cm (5'9") | 0.72 m | 28,986 steps |
| 180 cm (5'11") | 0.75 m | 28,180 steps |
| 185 cm (6'1") | 0.77 m | 27,419 steps |
| 190 cm (6'3") | 0.79 m | 26,697 steps |
Stride ≈ height × 0.414 (m).
How we calculate this (worked example)
Every figure on this page is produced by the same calculation engine as the calculator above — no hardcoded numbers. Here is the full arithmetic for 28,378 steps at 70 kg (154 lbs), moderate pace, flat ground.
- Distance: 28,378 steps × 0.74 m ÷ 1,000 = 21.00 km (13.05 miles)
- Walking time: 21.00 km ÷ 5 km/h × 60 = 4h 12m (252 minutes)
- Calories: 3.5 MET × 70 kg × 3.5 ÷ 200 × 252 min = 1,080 kcal
- Per step: 1,080 kcal ÷ 28,378 steps = 0.038 kcal per step
28,378 steps by body weight
| Body weight | Distance | Walking time | Calories burned |
|---|---|---|---|
| 55 kg (121 lbs) | 21.00 km (13.05 mi) | 4h 12m | 849 kcal |
| 70 kg (154 lbs) | 21.00 km (13.05 mi) | 4h 12m | 1,080 kcal |
| 85 kg (187 lbs) | 21.00 km (13.05 mi) | 4h 12m | 1,312 kcal |
| 100 kg (220 lbs) | 21.00 km (13.05 mi) | 4h 12m | 1,543 kcal |
Distance and time are identical across weights (21.0 km at 0.74 m stride) because only energy expenditure scales with body mass.
Definitions
- Step
- One single footfall. Two steps make one full stride cycle, so a pedometer counting 10,000 steps records 5,000 complete left-right cycles.
- Stride length
- The horizontal distance covered by one step, measured heel-to-heel. We use 0.74 m (2.43 ft) as the average adult value, or 0.415 × height in cm for men and 0.413 × height for women.
- Walking distance
- Steps × stride length. Distance in kilometres = (steps × stride in metres) ÷ 1,000; miles = kilometres × 0.621371.
- Calories burned
- Energy expenditure estimated with the MET equation: kcal = MET × weight (kg) × 3.5 ÷ 200 × minutes. Moderate walking at 5 km/h is MET 3.5.
- Walking time
- Distance ÷ walking speed. At the 5 km/h baseline, one kilometre takes 12 minutes and one mile takes about 19 minutes.
- Cadence
- Steps per minute. A moderate 5 km/h pace corresponds to roughly 100–110 steps per minute; brisk walking is 120+ steps per minute.
Assumptions and rounding rules
| Parameter | Default | Rule |
|---|---|---|
| Stride length | 0.74 m (2.43 ft) | Average adult; overridden by your height or entered stride |
| Walking pace | 5 km/h (3.1 mph) | Moderate, flat ground; reduced 20% on hills and 30% on trails |
| MET value | 3.50 | Flat terrain, moderate fitness; +0.1 MET per 1% incline |
| Body weight | 70 kg (154 lbs) | Reference weight for examples; your input replaces it |
| Distance rounding | 2 decimals (km and miles) | Rounded for display only — full precision is used in the maths |
| Calorie rounding | Nearest whole kcal | Rounded at the last step, never mid-calculation |
| Step rounding | Nearest whole step | Reverse calculations round to the nearest integer step |
Limitations
- All results are estimates, not measurements. MET-based calorie models typically fall within ±10–20% of indirect calorimetry for an individual.
- Individual differences in gait efficiency, age, body composition and fitness change actual energy cost at the same speed.
- Terrain, surface softness, wind and altitude are only partly captured by the terrain and incline settings.
- Stride length varies with pace, footwear and fatigue; a single average stride cannot represent a whole walk.
- Pedometers and phone accelerometers miscount steps by roughly 5–15%, especially at slow speeds or when carried in a bag.
- Figures describe activity energy expenditure only and exclude resting metabolism, so they should not be subtracted twice from a daily budget.
Method: stride-based distance plus the MET equation from the Compendium of Physical Activities (Ainsworth et al.). Results are estimates — see our estimation disclaimer.
How pace changes your 28,378-step walk
Leisurely
315 min
at 4 km/h
Moderate
252 min
at 5 km/h
Brisk
194 min
at 6.5 km/h
Calorie estimates use a 70 kg (154 lb) reference. Enter your own weight above for exact numbers.
28,378 steps vs the classic 10,000-step goal
That's 100% of a full 10,000-step day — do this 1× to hit the daily target.
100%
of 10k
Weekly
198,646
steps if daily
Monthly
851,340
steps if daily
Yearly km
7,665
if daily
Key takeaway
21 km ≈ 28,378 steps (13.05 miles), takes about 4h 12min at moderate pace, and burns ~1080 kcal for a 70 kg adult.
Want your exact number?
Real-Life Scenarios
🟢 Everyday — 21 km walked once through
Priya (65 kg) walks 21 km from the station home. It takes about 4h 12min and burns ~1003 kcal. Step count on her watch: ~28,378.
🟡 Weekend loop — 21 km with variable terrain
Mark (80 kg) takes 21 km along a mixed path. Elevation and softer ground push burn from ~1235 to ~1544 kcal.
🔴 Fitness plan — 21 km slotted into a weekly schedule
Julie (70 kg) walks 21 km 5×/week. Weekly kcal: ~5400. Weekly distance: 105.0 km.
In summary: 21 km ≈ 28,378 steps (13.05 miles), takes about 4h 12min at moderate pace, and burns ~1080 kcal for a 70 kg adult.