Math & Numbers
Compute the available Net Positive Suction Head (NPSH_a) of a pump and compare it against the required NPSH (NPSH_r) from the pump curve. Head-balance form: NPSH_a = (p_surface_abs - p_vapor) / (ρ·g) + H_static - h_friction. Surface and vapor pressures are absolute; H_static is positive for flooded suction, negative for suction lift. Returns margin (NPSH_a - NPSH_r), ratio (NPSH_a/NPSH_r) and a classification: safe, marginal (margin < 0.5 m), or cavitation likely. If NPSH_r = 0, only NPSH_a is reported. Pressure in Pa/kPa/bar/atm/psi, length in m/ft, density in kg/m³/g/cm³/lb/ft³.
pump-npsh-calculatorMath & Numbers
Size the shunt capacitor needed to raise the power factor: C = P·(tanφ₁ − tanφ₂)/(2π·f·U²). Returns compensated reactive power Qc, capacitive reactance Xc, capacitor current Ic, and the required capacitance in F/μF.
power-factor-correctionMath & Numbers
Calculate the Rankine passive earth pressure on a smooth vertical wall backfilled with cohesionless soil. K_p = tan²(45°+φ/2). Optional uniform surcharge q. Returns the base pressure p₀, the total force P, and the resultant height. Note: theoretical K_p is an upper bound; designers often apply a reduction factor for wall friction.
passive-earth-pressureMath & Numbers
Calculate the overall efficiency of a multi-stage transmission. η_total = η₁·η₂·…·ηₙ. Enter one stage efficiency per line (decimal, e.g. 0.98). Optionally add an input power to get the total loss and per-stage output power.
power-transmission-efficiencyFinance
Discount a future lump sum or an annuity back to today's value (PV). Supports lump-sum and annuity cash flows, multiple compounding frequencies, a present-value decay curve, and a per-period breakdown. PV = FV / (1+r)^n for a lump sum.
present-value-calculatorMath & Numbers
Solve pressure, force, or area from P=F/A, and convert between Pa, kPa, MPa, bar, atm, psi, Torr, inHg, kgf/cm²
pressure-conversionMath & Numbers
Compute gravitational potential energy, mass, or height from the other two, with impact velocity
potential-energy-calculatorMath & Numbers
Compute range, max height, flight time, and the full trajectory of a projectile given speed, angle, and optional initial height
projectile-motion-calculatorMath & Numbers
Convert pounds per square inch to bar with configurable decimal precision
psi-to-barMath & Numbers
Convert pounds per square inch to kilopascals with configurable decimal precision
psi-to-kpaMath & Numbers
Convert running pace in minutes per kilometer to kilometers per hour
pace-min-per-km-to-kmhMath & Numbers
Convert running pace in minutes per mile to miles per hour
pace-min-per-mile-to-mph