Engineering Calculators
Eight free field calculators for haulage, blasting, conveying, crushing, pit design, and project economics. Each one shows its formula.
These are the field numbers mine and plant engineers run every week. Each one shows the formula it uses, so you can check the math. For tonnage, stockpile, and trucking cost, use the Toolbox.
Rimpull & retarding force
Rule of thumb: 20 lb of force per ton of weight per 1% of grade. Rolling resistance adds to the grade uphill and subtracts from it downhill.
Loader–truck match
Passes are rounded down so the truck is not overloaded. Trucks are rounded up so the loader does not wait.
Max charge weight per delay
OSMRE scaled distance: W = (D ÷ Ds)². Ds is 50 to 300 ft, 55 to 5,000 ft, and 65 beyond 5,000 ft (30 CFR 816.67). Use a delay of 8 ms or more.
Burden, charge, and powder factor
Konya burden: B = 3.15 × De × (SGe ÷ SGr)^(1/3). Loading density = 0.3405 × SGe × De² lb/ft. The charge column is hole depth minus stemming.
Conveyor horsepower
Lift hp = tph × lift (ft) ÷ 990. The friction allowance is a screening percentage. Use CEMA methods for final design.
Crusher annual output
Annual tons = rated tph × availability × utilization × operating hours. Reduction ratio = feed size ÷ product size.
Stripping ratio & break-even SR
BESR = (price − royalty − mining and processing cost) ÷ stripping cost. Do not divide by swell: stripping is costed per bank yard.
Quarry NPV (straight-line depreciation)
ATCF = (revenue − cost)(1 − t) + t × depreciation. Depreciation is not cash; its only cash effect is the tax it saves.
Need a stamped number, not a screening number?
We do pit and plant design reviews, fleet studies, blast design, and project economics for operators and buyers.
Screening calculators for education and early planning. They do not replace site data, manufacturer performance charts, or an engineer's design.