Builds the true final price as a waterfall: stacked discounts, correct sales-tax base and cascade, tipping on the etiquette base with rounding, per-person split, and mid-market vs DCC conversion.

Math & Numbers

Transportation Problem Solver (Min-Cost Flow)

Balanced transportation problems as min-cost flow: successive shortest paths, MODI duals, reduced-cost optimality certificate, and full shipping plan.

Finance

Treasury Yield-Curve Nelson-Siegel / Svensson Bootstrap

Bootstrap the discount-factor and spot curve from treasury quotes, fit Nelson-Siegel or Svensson parametrically, and chart spot plus instantaneous forward curves with basis-point residuals.

Math & Numbers

Venn Diagram Problem Solver (Set Cardinality)

2-set and 3-set inclusion-exclusion solver: every disjoint region, the union, and the outside count, with consistency checks.

Math & Numbers

Torque Unit Converter (N·m / lbf·ft / kgf·m / lbf·in)

Convert torque (moment of force) between N·m (SI base), lbf·ft (pound-foot), kgf·m (kilogram-force-metre), and lbf·in (pound-inch). Factors based on standard gravity g₀ = 9.80665 m/s² and 1 lbf = 4.4482216152605 N. Converts via N·m to the target unit and also lists the equivalent value in all four units for reference. Used for mechanical specs, automotive, and fastener tightening torque.

Math & Numbers

Ventilation Rate Calculator (People / Area / Contaminant)

Compute the required outdoor / supply ventilation rate. ASHRAE 62.1 ventilation-rate procedure: people component Vpz = Rp·P, area component Vaz = Ra·A, breathing-zone outdoor air Vbz = Vpz + Vaz, zone supply airflow Voz = Vbz / Ez. Three modes: ASHRAE 62.1 (people + area), per-person rate (P × Rp), or contaminant dilution (Q = G / (C_acc − C_sup), where G can be mg/s, mg/h, or L/s of gas and concentrations mg/m³ or ppm). Results reported in L/s, m³/h, and CFM.

Math & Numbers

Three-Phase Power Calculator

Calculate active, reactive, and apparent power for a balanced three-phase system: S=√3·U·I, P=√3·U·I·cosφ, Q=√3·U·I·sinφ. Also returns the power-factor angle φ and verifies the power triangle.

Math & Numbers

Transformer Impedance Transfer Calculator

Reflect an impedance through an ideal transformer: Z' = a²·Z, where a = N₁/N₂. Supports secondary→primary and primary→secondary directions; a can be given directly or derived from N₁/N₂. Also returns admittance Y and reflected admittance.

Math & Numbers

Transformer Turns Ratio Calculator

Ideal transformer ratio: a = N₁/N₂ = V₁/V₂ = I₂/I₁. Given turns, voltage, or current on either side, compute a and the corresponding voltage/current on the other side; verifies V₁·I₁ = V₂·I₂.

Math & Numbers

Torque Calculator (τ = rF sinθ)

Compute torque, force, or lever arm from τ = r·F·sin(θ), with the perpendicular force component shown

Calculator

Tile Coverage Estimator

Estimate how many tiles you need to cover a room, including layout-aware waste (straight, 45° diagonal, herringbone, basketweave), boxes to buy, grout volume and weight, and an optional cost total. Enter room and tile dimensions plus joint width to get a ready-to-order material list.

Calculator

Tire Size & Gear Ratio Calculator

Enter a tire size (285/70R17), differential/final-drive ratio, and transmission gear ratios to compute the true overall tire diameter, circumference, revolutions per mile/km, an RPM × gear speed table, effective final drive after a tire change, and speedometer error. Metric or imperial units, with optional before/after tire comparison.