🧮Calculators
Calculators cover finance, health, math, physics, engineering and everyday life: interest and loans, net salary, BMI, rule of three, conversions and more. Results are informational and educational — for important decisions, confirm with a professional and official sources.
2826 tools
Rule of 72 (Investment Doubling)
Estimate years needed to double an investment at an annual rate using the classic Rule of 72. Compare with exact (ln 2 / ln(1+r)).
Capital Equivalence Calculator
Check whether two payment streams are equivalent at a given rate, by bringing all to a focal date (date zero).
Yearly ↔ Monthly Rate Equivalence
Convert compound interest rates between periods (annual, monthly, daily, semi-annual). i_year = (1+i_month)^12 - 1.
Leasing with Residual Calculator
Compute monthly leasing payment with residual value at term end, given rate, periods and optional down payment.
Bullet Loan Calculator
Bullet loan: pay only interest during the term and the principal at the last period. Compute total interest and schedule.
Personal Loan Interest
Compute installment and total interest of a personal loan via Price system, given principal, rate and term. Shows approximate CET.
Mortgage Payment Calculator
Compute monthly mortgage payment with down payment, rate, term (years) and insurance. Supports Price system.
Auto Loan Payment Calculator
Compute monthly auto loan payment: financed amount, rate and term. Shows total paid and interest.
Debt Refinance Savings
Compare two debt scenarios (current vs renegotiated) with different rates and terms; shows interest savings and monthly cash.
CDC Loan Calculator (Brazil)
Brazilian CDC consumer loan: monthly installment via Price with monthly nominal rate and short term (3-60 months).
Cubic ↔ Square Feet Converter
For an area in square feet (sqft), multiply by height to get cubic feet. Useful in ventilation and logistics.
Concrete Mix Calculator
Estimate cement, sand, gravel and water for a given concrete amount based on the mix ratio (e.g., 1:2:3) and target volume.
Backfill Belt Calculator
Volume of backfill for a foundation belt, given width, height and total perimeter length.
Raft Foundation Volume
Volume of concrete for a raft foundation: width × length × thickness, optional 5% overage.
Swimming Pool Volume
Compute rectangular or cylindrical swimming pool volume in liters and m³. Useful for chlorine and chemical dosing.
Water Tank Volume Calculator
Compute rectangular and cylindrical water tank volume in liters. Suggests minimum size for N people (200L/day/person).
Pipe Pressure Loss Calculator
Pipe head loss via Hazen-Williams: J = 10.67 × Q^1.85 / (C^1.85 × D^4.87). For water at 20°C.
Short-Circuit Current Calculator
Estimate symmetric single-phase short-circuit current at low-voltage points from transformer and cable impedance.
Breaker Sizing Calculator
Suggest a standard breaker (6, 10, 16, 20, 25, 32, 40, 50, 63 A) from circuit power and voltage (110/220V).
Electrical Cable Section (mm²)
Compute minimum recommended cable section (1.5, 2.5, 4, 6, 10, 16, 25 mm²) by current and installation type (NBR 5410 simplified).
Residential Lighting (W/m²)
Suggest total lighting wattage and number of LED bulbs per room based on 100 lux/m² standard for bedrooms/living rooms.
Pipe Flow Rate Calculator
Compute flow rate Q = A × v given internal diameter and fluid velocity. Output in L/s, m³/h and gpm.
Pump Power (HP)
Compute hydraulic and electric power (HP) of a pump given flow, head and efficiency.
Sprinkler Nozzle Flow
Compute sprinkler nozzle flow Q given pressure and discharge coefficient Cd. Q = Cd × A × √(2gh).
Pneumatic Cylinder Force
Compute extend and retract forces of a pneumatic cylinder: F = P × A. Uses annular area for retract.
Gear Ratio Calculator
Compute gear ratio Z_out/Z_in for a gear pair, output RPM and resulting torque.
Belt Center Distance Calculator
Compute center distance between two pulleys for a given belt length using Liter's approximation.
Bearing Life L10
Compute nominal bearing life L10 in million revs: L10 = (C/P)^p with p=3 (ball) or p=10/3 (roller).
Helical Spring Rate
Compute helical compression spring rate: k = G·d⁴/(8·D³·N), with G shear modulus.
Pipe Working Pressure
Maximum working pressure of a thin-wall cylindrical pipe via Barlow's formula: P = 2·t·S/D.
Beam Deflection (Center Load)
Compute max deflection δ = PL³/(48EI) of a simply-supported beam with center point load.
Rectangular Section Inertia
Compute Ix and Iy of a rectangular section: Ix = b·h³/12, Iy = h·b³/12. Also section modulus W.
Beam Deflection (Uniform Load)
Max deflection δ = 5wL⁴/(384EI) of simply-supported beam with uniformly distributed load. Useful for basic structural sizing.
Trapezoid Area & Diagonals
Compute area, perimeter, diagonals and midline of a trapezoid from bases and height. Supports isosceles trapezoid too.
Polygon Shoelace Area
Compute simple polygon area (non self-intersecting) using the Shoelace formula given vertices (x,y).
Ellipse Perimeter (Ramanujan)
Ramanujan's approximation for ellipse perimeter: P ≈ π[3(a+b) − √((3a+b)(a+3b))]. More precise than (2π·avg).
Circle Chord & Height
Compute chord c and sagitta (height) h of a circle arc given radius r and angle θ (or arc length s). c = 2r·sin(θ/2), h = r − r·cos(θ/2).
Circular Segment Area
Circular segment area (between chord and arc) given radius r and angle θ. A = r²·(θ − sin θ)/2.
Annulus Area
Annulus area between outer R and inner r radii: A = π(R² − r²). Useful for pipes and gears.
Ellipse Area & Perimeter
Compute area A = π·a·b and approximate perimeter (Ramanujan) of an ellipse from semi-axes a and b.
Torus Volume & Surface
Compute torus volume V = 2π²·R·r² and surface S = 4π²·R·r, where R is major radius and r minor.
Cone Frustum (Volume + Lateral)
Compute cone frustum volume V = πh(R² + r² + R·r)/3 and lateral area A_lat = π(R+r)·g (g = slant).
Prism Volume & Surface
Compute volume V = A_base·h and total surface = 2·A_base + perimeter·h for prisms with regular N-gon base.
Regular Tetrahedron Volume
Compute volume V = a³/(6√2) and total area A = √3·a² of a regular tetrahedron with edge a.
Depth of Field Calculator
Calculate depth of field from aperture, focal length and subject distance. Result in meters: near, far and total distance.
Beer ABV Calculator
Calculate alcohol content (ABV %) from original gravity (OG) and final gravity (FG) using the standard homebrewing formula.
RT60 Reverberation Calculator
Calculate reverberation time RT60 using Sabine's formula: T = 0.161 · V / A. Useful for studio, room and auditorium acoustics.
Board Feet Calculator
Convert lumber dimensions to board feet (BF), traditional US unit: 1 BF = 144 cubic inches (12"×12"×1").
Irrigation Flow Calculator
Calculate irrigation flow in L/h and mm/h from irrigated area, dripper count and unit flow. Useful for agricultural hydraulic projects.
Planting Density Calculator
Calculate plants per hectare from row spacing and plant spacing. Essential for agricultural planning.
Lens FOV Calculator
Calculate the angular field of view of a full-frame (35 mm) lens from its focal length. Returns horizontal, vertical and diagonal FOV in degrees.
Lux Illumination Calculator
Calculate illuminance (lux) from luminous flux (lumens) and area (m²). Includes reference values for offices, rooms and spaces.
Retirement: Contribution Time vs Points
Compares retirement rules by contribution time and by points (age + time) in the Brazilian pension reform.
Exponential Decay Calculator
Applies N = N0 * e^(-k*t) to compute remaining value in exponential decay.
Monthly Compound Interest Calculator
Compounds principal with monthly deposits at monthly rate over months.
Money Doubling Time (Rule of 72)
Applies the Rule of 72 to estimate how many periods until money doubles at a given rate.
Bond Yield (Coupon)
Estimates approximate yield-to-maturity of a coupon bond from face, price, and term.
Net Margin Calculator
Computes net margin percentage from net profit and total revenue.
Markup & Selling Price Calculator
Calculate a product selling price from its cost and the desired markup. Set the right margin to cover expenses and lock in your business profit.
Pediatric BMI Calculator
Computes child BMI and classifies in a simplified WHO band by age.