MathBench

Calculators that show their work

Every MathBench tool gives you the answer and the formula, a worked example, and the assumptions behind it — so you can trust the number before you order materials or make a plan.

All calculators

  • Calorie Calculator

    Daily calorie needs from the Mifflin-St Jeor equation — resting rate, maintenance, a goal target, and a macro split, with the uncertainty stated.

  • BMI Calculator

    Body mass index with your healthy weight range, the WHO and Asian threshold scales, and waist-to-height ratio alongside it.

  • Body Fat Calculator

    Body fat percentage from tape measurements by the US Navy method, with fat and lean mass and the error stated honestly.

  • Calories Burned Calculator

    Energy cost of an activity from MET values, with gross and net shown separately and a correction for the resting rate the standard formula assumes.

  • Concrete Calculator

    Slabs, footings, and round columns — cubic yards plus 60 lb and 80 lb bag counts.

  • Gravel Calculator

    Area and depth to cubic yards and tons, with density presets for crushed stone, pea gravel, and sand.

  • Mulch Calculator

    Rectangular and circular beds to cubic yards and bag counts at your chosen depth.

  • Paint Calculator

    Room size to gallons — wall area minus doors and windows, per coat, at your paint’s coverage rate.

  • Roofing Calculator

    Footprint and pitch to roof area, shingle squares, and bundle counts with waste included.

  • Board Foot Calculator

    Thickness, width, length, and quantity to board feet — with total cost at your price per BF.

  • Stair Stringer Calculator

    Total rise to riser height, tread count, total run, and stringer length — with code checks.

  • Fence Calculator

    Run length and post spacing to posts, rails, pickets, and concrete bags.

  • Room Lumen Calculator

    How much light a room needs — foot-candles or lux to total lumens and bulb count, with room shape and surface reflectance accounted for.

  • dBm to Watts Calculator

    Convert between dBm and watts or milliwatts in either direction, with a common-values table.

  • VSWR Calculator

    Enter any one of VSWR, return loss, reflection coefficient, or mismatch loss to get the rest.

  • Coax Cable Loss Calculator

    Cable type, length, and frequency to dB loss and power delivered — RG and LMR presets included.

  • Microstrip Impedance Calculator

    Trace width, substrate height, and εr to Z₀ — or solve for the width that hits a target impedance.

  • Pipe Pressure Drop Calculator

    Pressure drop from flow rate and pipe size — Darcy-Weisbach with fitting losses, elevation, and temperature-dependent liquid and gas properties.

  • Heat Transfer Calculator

    Conduction, convection and radiation for HVAC — wall and roof U-values with air films and framing, pipe insulation, and surface heat flow.

  • Heat Sink Calculator

    Size a heat sink from the junction-to-ambient thermal resistance network, or find the junction temperature a sink you already have will allow.

  • Sensible & Latent Heat Calculator

    Split an HVAC load into sensible and latent parts — airflow, temperature rise and humidity change to Btu/h, with the 1.08 and 0.68 constants derived rather than assumed.

  • Reynolds Number Calculator

    Velocity, pipe diameter, and fluid viscosity to Reynolds number with a laminar/turbulent verdict.

  • Dilution Calculator (C₁V₁ = C₂V₂)

    Solve for any of stock concentration, stock volume, final concentration, or final volume — unit-aware.

  • Molarity Calculator

    Mass, molecular weight, and volume to molarity — solve for any, with common reagent MW quick-picks.

  • Projectile Motion Simulator

    Animated launch with air drag — enter the push, mass, angle, and site conditions; get the flight path equation, range, zenith, and time to land.

  • Tithing Calculator

    A tithe per paycheck and per year, on gross or take-home pay — plus what it actually costs you after tax.

  • Mortgage Calculator

    Full monthly payment — principal & interest plus taxes, insurance, PMI, and HOA — with a breakdown chart, amortization schedule, and payoff date.

  • Mortgage Payoff Calculator

    See how extra monthly or one-time payments change your payoff date and total interest — with a chart.

  • Biweekly Mortgage Calculator

    Compare a standard monthly schedule against biweekly half-payments — time and interest saved.

  • HELOC Payment Calculator

    Interest-only and repayment-phase payments for a HELOC draw, plus the payment jump between them.

  • Home Sale Proceeds Calculator

    Sale price minus commission, payoff, closing costs, and concessions — your estimated net at closing.

  • 401k Early Withdrawal Calculator

    Penalty, federal, and state taxes on an early withdrawal — what you keep and what it really costs.

  • Self-Employment Tax Calculator

    SE tax on net profit with the 2026 Social Security wage base, the half-SE-tax deduction, and a quarterly set-aside.

  • Plywood Cut List Optimizer

    Nest your parts onto sheets with a real blade kerf — sheet counts, cut diagrams, offcuts, and an Excel export.

  • Engineering Unit Converter

    Convert across 24 quantities — every factor exact, derived from defining constants, and sourced.

  • Multiphase Flow Analyzer

    Gas–liquid pressure drop, void fraction, flow regime, and boiling or condensing heat transfer along the pipe.

  • Compound Interest Calculator

    Principal, contributions, rate, and time to final balance — with the growth curve charted.

  • Retirement Age Calculator

    Savings, contributions, and spending target to the age your nest egg supports retirement.

  • Ad Revenue Calculator

    Pageviews and RPM — or CTR and CPC — to monthly and yearly earnings for Google and Meta publishers.

  • Quadratic Equation Solver

    Roots (real or complex, in exact and decimal form), discriminant, vertex, and factored form — with every step shown.

  • Complete the Square Calculator

    Transform ax² + bx + c into vertex form step by step, with exact fractions at every stage.

  • t-Test Calculator

    One-sample, Welch two-sample, or paired — t statistic, degrees of freedom, and exact p-values from your data.

  • Chi-Square Test Calculator

    Goodness of fit and independence tests with expected counts shown and small-cell warnings.

  • Plot Digitizer (Graph → Data)

    Turn a picture of a chart back into numbers: calibrate the axes, click the points, export CSV.

  • Random Team Picker

    Split any list of names into fair random teams — unbiased shuffle, by team count or team size.

  • Spinner Wheel

    Add your options, spin the wheel, get a fair pick — the result comes from an unbiased RNG, not the animation.

  • Coin Flip

    Flip one coin or twenty — fair 50/50 flips with a running tally, streak tracking, and the real math of runs.

  • Blackjack Odds Calculator

    Exact dealer bust rates by upcard and the true EV of standing, hitting, or doubling any hand.

  • Poker Odds Calculator

    Outs to exact turn and river odds, the rule of 2 & 4 checked, and pot-odds break-evens for Hold’em.

  • Pool Chemical Calculator

    Chlorine, pH, alkalinity, calcium, and stabilizer doses for pools and spas — with a saturation-index verdict.

  • Circle Skirt Calculator

    Waist and length to the exact drafting radii — full, ¾, half, or quarter circle — plus yardage.

  • Quilt Calculator

    Backing yardage with the thriftier seam direction, the right precut batting, and binding strips.

  • Curtain & Drapery Calculator

    Rod width and fullness to fabric drops, repeat-matched cut lengths, and total yardage.

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