Free Field Math
DIRTby SubTrack
Trench and excavation volumes, swell, haul cycles, aggregate tonnage, stockpiles, grades, and conversions. No login. Built for earthworks crews who bill T&M.
Field calculators
Estimates for bidding and the truck. Confirm against survey, geotech, and scale tickets before you price.
Trench volume
Excavated volume of a linear trench. Use battered sides for open-cut walls.
Length
m
Bottom width
m
Depth
m
Side slope (H : 1V)
0.5 = 1H:2V. Ignored if sides are vertical.
Excavated volume
72m³
Top width
1.8m
Spoil typically swells 20–30%. Use Swell & shrink to size the stockpile, then Trucks & haul for loads.
Calculators with a formula and an example
Trench volume calculator
Volume = length × average width × depth. For a battered trench, average width = bottom width + side-slope × depth, and top width = bottom width + 2 × side-slope × depth. Side slope is run per unit of rise (for example 1:1 is 1).
A 40 m run, 0.9 m bottom, 1.2 m deep, 1:1 sides: average width is 2.1 m, volume is 100.8 m³ bank. Convert to loose with the swell calculator before you count trucks.
Swell and shrink calculator
Loose = bank × (1 + swell). Compacted = bank × (1 − shrink). If you know loose, bank = loose / (1 + swell). Load factor is 1 / (1 + swell).
100 bank m³ of common earth at 25% swell is 125 loose m³. At 12% shrink, compacted is 88 m³. A truck that holds 12 loose m³ needs about 11 loads, not 9.
Haul cycle and truck calculator
Loose volume = bank × (1 + swell). Load carried = min(box, payload / density). Loads = loose / load carried. Cycle minutes = load + haul + return + dump. Trucks = ceil(total truck-hours / shift hours).
800 bank m³, 25% swell, 12 m³ box, 16 t payload, 1.28 t/m³ loose: the truck is weight-capped at about 12.5 m³, so use 12 m³. That is about 83 loads. A 28-minute cycle is roughly 2.1 loads per hour.
Aggregate tonnage calculator
Volume = length × width × depth. Tonnes = volume × density (t/m³). Short tons = tonnes × 1.102. Use compacted density for placed base, loose density for a stockpile.
A 60 m × 4 m lane, 150 mm of compacted road crush at 2.24 t/m³ is 36 m³ and about 81 tonnes. Order a little extra for waste and the last truck.
DIRT FAQ
What is bank versus loose volume?
Bank is in the ground. Loose is after you dig it. Trucks haul loose. Pay quantities are often bank. Use the swell calculator before you count loads.
What swell factor should I use?
Sand and gravel are often near 12%, common earth near 25%, clay near 30%, blasted rock near 50%. Confirm with the cut and the scale ticket.
Does DIRT do metric and imperial?
Yes. Switch units on any calculator. Formulas stay the same. Only the labels change.
How does this become a billable ticket?
DIRT sizes the dirt. SubTrack rate sheets lock excavator, truck, and labor rates. The LEM is what the client signs.
Field cheat sheet
Print a one-page formula sheet for the truck. Figures are typical ranges. Confirm with site and scale-ticket data.
The math is free. The ticket still has to get paid.
DIRT sizes the work. SubTrack turns the labor, iron, and material on the job into a signed LEM and an invoice.