About

Miscalculating troop movement time leads to broken supply lines, missed coordination windows, and force fragmentation. Historical doctrine from FM 21-18 and ATP 3-21.18 establishes baseline march rates of 4 km/h for dismounted infantry under ideal conditions. Real terrain rarely cooperates. A dense forest reduces effective speed by a factor of 0.4. Mountain passes with snow compound that to 0.15 of base rate. This calculator applies layered coefficients for terrain type (K_t), weather (K_w), unit size (K_s), and cumulative fatigue (K_f) to produce a corrected march time that includes mandatory rest halts per doctrinal standards.

The tool approximates travel under sustained march conditions and assumes no enemy contact. It does not account for METT-TC variables beyond terrain and weather. For mechanized units, speeds reflect road-march averages rather than cross-country sprint capability. Pro tip: always add 15 - 20% buffer to calculated times for assembly, river crossings, and navigation errors in low-visibility conditions.

Formulas

Effective march speed is the product of the base rate and four independent correction coefficients. Total travel time includes doctrinal rest halts.

V_eff = V_base × K_t × K_w × K_f × K_s

T_march = DV_eff

T_rest = floor(T_march) × 10 min + floor(T_march4) × 60 min

T_total = T_march + T_rest

Where V_base = base march speed for the unit type (km/h), D = total distance (km), K_t = terrain coefficient (0.20 - 1.00), K_w = weather coefficient (0.30 - 1.00), K_f = fatigue coefficient that decreases with march duration (starts at 1.00, decays to 0.70 after 8 h), and K_s = unit size coefficient reflecting column-length delays (0.75 - 1.00). Rest halts follow the 50/10 rule: 10 min rest per 50 min march, plus 1 h extended halt every 4 h.

Reference Data

Unit / Movement Type	Base Speed	Sustained Daily Range	Doctrine Source
Light Infantry (Foot March)	4.0 km/h	32 km	FM 21-18
Heavy Infantry (Full Kit >30 kg)	3.2 km/h	25 km	ATP 3-21.18
Forced March (Infantry)	5.5 km/h	50 km	FM 21-18
Cavalry / Mounted (Horse Walk)	6.0 km/h	40 km	Historical Avg
Cavalry / Mounted (Horse Trot)	13.0 km/h	55 km	Historical Avg
Wheeled Convoy (Road)	40.0 km/h	300 km	NATO STANAG
Tracked Vehicles (Road)	30.0 km/h	200 km	NATO STANAG
Tracked Vehicles (Cross-Country)	15.0 km/h	120 km	ATP 3-90
Mountain Troops (Alpine)	2.0 km/h	15 km	Mountain Warfare Manual
Ski Troops (Winter)	5.0 km/h	35 km	Nordic Doctrine
Supply / Logistics Train	3.0 km/h	20 km	FM 4-01.45
Artillery Battery (Towed)	25.0 km/h	150 km	FM 3-09
Amphibious (River Crossing)	6.0 km/h	30 km	FM 90-13
Airborne (Post-Drop Assembly)	3.5 km/h	20 km	FM 90-26
Terrain Modifiers (K_t)
Paved Road	1.00
Improved Trail / Gravel	0.85
Open Flat Ground	0.75
Rolling Hills	0.60
Light Forest / Woodland	0.55
Dense Forest / Jungle	0.35
Swamp / Marsh	0.25
Mountain / Steep Grade	0.30
Desert (Soft Sand)	0.45
Snow (Deep >30 cm)	0.30
Urban / Built-Up Area	0.50
River / Stream Crossing	0.20

Frequently Asked Questions

The terrain modifier assumes an average grade for the terrain type. Mountain terrain at K_t = 0.30 assumes sustained grades of 15-30%. For steeper grades exceeding 45%, effective speed drops further - roughly halved again. The Naismith rule adds 1 hour per 600 m of ascent to flat-equivalent time. This calculator uses aggregate coefficients rather than per-segment elevation analysis, so for routes with extreme elevation change, calculate each segment separately.

Larger formations create longer march columns. A battalion-sized column may stretch 3-5 km on a road. The tail of the column experiences accordion effects at every turn, obstacle, and halt - causing cumulative delays. The size coefficient K_s ranges from 1.00 for squad/platoon (under 50 personnel) down to 0.75 for brigade-level movements (3,000+ personnel). This reflects an average 15-25% time penalty documented in NATO road-march planning guides.

Yes. Selecting "Night March" applies an additional weather-category modifier of 0.60 for movements without night-vision devices, reflecting reduced visibility navigation speed. With NVDs, the penalty is approximately 0.80. Historical data from FM 21-18 shows night marches average 60-70% of daytime rates for trained troops and as low as 40% for poorly trained units.

The fatigue coefficient K_f starts at 1.00 and decays linearly. After 4 hours of sustained march, K_f drops to approximately 0.90. After 8 hours, it reaches 0.70. After 12 hours (forced march territory), it bottoms at 0.55. This models glycogen depletion and musculoskeletal fatigue observed in military exercise data. The calculator recalculates iteratively: each hour-segment uses the degraded speed, so total time is not a simple division.

The standard 50/10 rule: 10 minutes of rest for every 50 minutes of marching. Additionally, after every 4 hours of cumulative march time, a 1-hour extended halt is added for feeding, equipment checks, and medical attention. For forced marches, rest halts are reduced to 5 minutes per hour with no extended halts - this is reflected when selecting "Forced March" type. Total rest time is added to pure march time to produce the final ETA.

For vehicle convoys, the base speeds of 30-40 km/h reflect sustained averages including fuel stops, not burst speed. The terrain coefficient applies primarily to surface quality. Wheeled vehicles on unpaved roads drop to K_t = 0.50, while tracked vehicles handle rough terrain better at K_t = 0.65. The unit size penalty is more severe for vehicle convoys due to spacing requirements (50-100 m intervals). This tool provides planning estimates - actual convoy speeds depend heavily on road width, bridge classifications, and traffic control.