All calculators

WHO, Asia-Pacific, Japan & Korean standards

BMR & TDEE using Mifflin-St Jeor, Schofield (NHS), Harris-Benedict

Western age vs Korean age (만 나이)

Mifflin-St Jeor (US), Harris-Benedict, Katch-McArdle, NHS Schofield

Total daily energy expenditure with 6 activity levels — WHO, CDC, NHS

Hamwi, Devine, Robinson, Miller formulas + WHO BMI range vs Asia-Pacific

US RDA (0.8 g/kg) vs EFSA (0.83 g/kg) vs WHO (0.66 g/kg) vs sport nutrition (1.6–2.2 g/kg)

Protein/carbs/fat targets from TDEE — USDA, UK Eatwell, Australian, Keto

Daily hydration: US IOM (3.7L) vs EFSA Europe (2.5L) vs Australia (2.6L)

Max HR zones using Fox & Haskell, Tanaka, or Gulati (women) formula

Pace ↔ speed ↔ finish time — 5K, 10K, half marathon, marathon (km & miles)

Steps → km/miles/calories. The 10,000 steps origin — Japan 1965 marketing

Cardiorespiratory fitness from resting HR, Rockport, or Cooper test — AHA/ACSM norms

1RM using Epley, Brzycki, Lombardi, O'Conner + training % table (IPF standard)

WHO cardiovascular risk classification vs Japan metabolic syndrome criteria

Boer & Hume formulas — used for clinical drug dosing globally

US Army circumference method (AR 600-9) vs UK/AU/CA military standards

Blood alcohol: US 0.08% vs Japan 0.03% vs Germany 0.05% driving limits

Estimate lifespan by country, smoking, BMI, exercise — Japan #1 at 84.3 years

EDD from LMP (Naegele's rule), conception, or IVF transfer — NHS, ACOG, WHO

Fertile window by cycle length — NHS, ACOG, Germany BZgA guidance

US Navy circumference method — body fat % from waist, neck & height

EDD from LMP or conception date — Naegele's rule (ACOG, NHS)

Best bedtime & wake-up time from 90-minute sleep cycles

Monthly payments, housing costs, extra principal and full amortization

US loans vs UK HP/PCP agreements vs Canada & Australia financing

Monthly payment and total cost — US, UK, Canada, Australia, Germany

US federal IDR plans, UK Plan 2/5, Australia HECS-HELP (no interest!)

Full month-by-month payment schedule for any loan

True APR including fees — US TILA vs EU APRC vs UK Consumer Credit Act

APY (US) vs AER (UK) — daily, monthly, annual compounding

Monthly payment & amortization for personal, auto, student loans

US CDs, UK fixed-rate bonds, AU term deposits, CA GICs — compare rates

Project growth with UK ISA, Canadian TFSA, Australian Super, or taxable account

ECB reference when available, dated snapshot otherwise — 28 currencies, not a bank quote

Home & car loan EMI — equated monthly installment with amortization

Purchasing power 1970–2026 — US CPI, UK RPI/CPI, EU HICP, Japan, Canada, Australia

Add or remove VAT & GST — UK 20%, EU rates, Australia 10%, India, Singapore

Sale price, percent off, original price — stacked discounts explained

Total and annualized return on investment — US CGT vs UK ISA vs AU 50% discount

PV of lump sum or annuity — US OMB 7% vs UK Green Book 3.5%

Grow savings with contributions — 401k, ISA, RRSP, Australian Super

Net present value for capital budgeting — enter any series of cash flows

Internal rate of return vs hurdle rate — private equity, real estate, projects

Dividend income and tax — US 0–20%, UK £500 allowance, AU franking credits

Total return with capital gains tax — US short/long-term, UK 18%/24%

Straight-line, 150% DB, Double Declining — US MACRS vs UK capital allowances

PV and FV of annuity payments — UK pension drawdown vs US annuity products

2026 contribution limits + employer match projection

Traditional vs Roth IRA side-by-side — UK ISA, CA TFSA, AU super equivalents

Required Minimum Distribution from IRA/401k using IRS Uniform Lifetime Table

Tax on investment gains — US 0/15/20%, UK £3K allowance, AU 50% discount, CA 50% inclusion

Statewide US rate as a starting point — not a ZIP engine. HST, GST, VAT as typed rates

US Schedule SE, UK Class 4 at 6%/2%, Canadian CPP both portions — federal/national only

Estimate US retirement benefits — PIA from AIME, FRA 67, early vs delayed claiming

Failure-to-pay/file penalties + interest, installment agreement costs

2.5% of zakatable wealth above nisab — gold, silver, cash, investments

Gross margin % from cost and revenue — margin vs markup explained

Selling price from cost and markup % — retail standards by industry

Gross profit, EBIT, and net profit margin from revenue and costs

Flat-rate and tiered commission — real estate, SaaS, insurance rates

Break-even units and revenue — contribution margin, SBA/UK loan requirements

US SBA 7(a), UK Start Up Loans, Australian small business financing

US 28/36 rule, UK 4.5× income, Canada stress test, Australia buffer

Compare total cost of renting vs buying — break-even point, equity

Minimum down by loan type — FHA 3.5%, conventional 20%, CMHC, LMI

US PMI monthly cost, Canada CMHC premium, Australia LMI — when it cancels

Break-even and lifetime savings — US closing costs, UK remortgage ERCs

US money factor lease payment vs UK PCP finance — vehicle financing

US mill rates (0.28–2.49%), UK Council Tax bands, AU land tax

US HYSA, UK Cash ISA, Canadian TFSA, Australian high-interest savings

4% rule nest-egg goal — UK pension, RRSP, Australian super

I = P × r × t — compare simple vs compound. Treasury bills globally.

Fixed vs minimum-only payments. US ~22.99%, UK ~20–25% APR explained.

Avalanche vs snowball method — compare strategies, see total interest

US 43% limit, UK affordability test, Canada TDS/GDS thresholds

See how minimum-only payments trap you — payoff timeline & total interest

Annual ↔ monthly ↔ hourly ↔ weekly conversion. Minimum wages by country.

Convert hourly wage to annual salary accounting for paid/unpaid time off

FLSA 1.5× (US), Working Time Directive (UK), NES (Australia)

50/30/20 rule budget planner with cost-of-living context by country

Assets minus liabilities. Compare to median net worth — Fed, ONS, ABS data.

Take-home pay after tax — US, UK, Canada, Australia

Federal tax + Social Security + Medicare (2026 brackets)

Income tax + National Insurance 2026/27 (HMRC rates)

Income tax for US, UK (with NI), and Canada

Tipping customs across 8 countries — including Japan (no tip)

Creator earnings from views & RPM — US, UK, India, Brazil CPM rates

sin, cos, tan, log, ln, √, x², factorials — deg & rad modes

Plot up to 6 functions simultaneously — polynomials, trig, exponentials, logarithms. Pan & zoom.

3 calculation modes: % of X, X is what % of Y, % change

Days, weeks, months, years between two dates

Add, subtract, multiply, divide, simplify fractions. Decimal ↔ fraction.

Solve a/b = c/d — cross-multiplication. EU 'Dreisatz / Règle de trois'.

Add, subtract, multiply, divide mixed numbers. Converts to improper fractions.

Check primality, list primes (Sieve of Eratosthenes), prime factorization

2×2 and 3×3 matrix add, subtract, multiply, transpose, determinant

nPr and nCr with steps. US C(n,r) vs UK ⁿCᵣ vs IB notation explained.

US 4.0 scale, UK Honours, German 1–4, Australian HD

Bidirectional 1–3999 conversion — subtractive notation explained

Add, subtract, magnitude, unit vector — 2D, 3D & 4D vectors with steps

Scalar product A·B and angle between vectors — 2D to 5D

3D vector product A×B — perpendicular vector, parallelogram area, right-hand rule

Project A onto B — parallel & perpendicular components. Used in PCA & least squares.

Multiply matrices of any size — 2×2 to 4×4 with general dimensions

2×2 to 5×5 determinant via cofactor expansion (2/3×3) & LU decomposition (4/5×5)

2×2 to 4×4 inverse via Gauss-Jordan. Detects singular matrices. Row operations shown.

Reduced Row Echelon Form — rank, nullity, and pivot columns. Rank-nullity theorem.

2×2 and 3×3 eigenvalues via characteristic polynomial. Normalized eigenvectors.

Orthogonalize vectors to create orthonormal basis. QR decomposition foundation.

Null space basis & column space basis from RREF. Rank-nullity theorem demonstrated.

Transpose any matrix (2×2 to 5×5). Detects symmetric matrices. Shows A^T = A cases.

Check up to 5 vectors (ℝ²–ℝ⁴) for linear independence via RREF. Finds basis for span.

Circle, rectangle, triangle, trapezoid, ellipse, parallelogram — m² & ft²

Sphere, cylinder, cone, cube, prism — litres, US gallons, UK gallons

Solve any triangle — SSS, SAS, AAS. Law of sines & cosines.

a² + b² = c². Find any side. Pythagorean triples. 4 independent discoveries.

Radius, diameter, circumference, area — solve from any one value. π explained.

Solve ax²+bx+c=0. Discriminant, complex roots, vertex. Germany's 'Mitternachtsformel'.

√x, ∛x, nth root. Simplifies radicals (√48 = 4√3). Perfect squares.

xⁿ for any base and exponent. Negative & fractional powers. Scientific notation.

log₁₀, ln, log₂, and any custom base. Change-of-base formula.

n! exact up to n=5000. Double factorial, Stirling's approximation.

Greatest Common Factor (HCF/GCD) and LCM for 2+ numbers. Prime factorization steps.

Simplify ratios, scale them, or solve a:b = c:d proportions. Rule of three.

Step-by-step long division with remainder. US (÷) and European (:) notation.

Round to decimal places, sig figs, or nearest n. Banker's rounding (IEEE 754).

Count sig figs or round to n sig figs. IB/AP/A-Level rules explained.

Integers, decimals, dice rolls, or random picks from a set. Seeded & unique modes.

Binary ↔ Octal ↔ Decimal ↔ Hex with step-by-step. Unix permissions, CSS colors.

Mean, median, mode, std dev (sample & population), variance, IQR

All 3 averages + range from any data set. Why governments use median income.

Population (÷n) and sample (÷n−1) variance & std dev. Bessel's correction explained.

Z-score and percentile. Left/right/two-tailed probabilities. Japanese hensachi.

P-value from z or t score. One/two-tailed. α = 0.05 / 0.01 significance levels.

CI for mean or proportion at 90/95/99%. Auto t-distribution for n < 30.

Required survey sample size. Finite population correction for small communities.

Pearson r, Spearman ρ, R², linear regression. AP Stats, A-Level, IB.

P(A∪B), P(A∩B), P(A|B), P(A'). Frequentist rules for AP Stats / A-Level.

Population (σ) and sample (s) std dev with step-by-step working

Celsius, Fahrenheit, Kelvin, Rankine with reference table

Length, weight, volume, area — metric & imperial

mm, cm, m, km, in, ft, yd, miles, nautical miles, furlongs — 17 units

kg, lbs, stone (UK), oz, tonnes, troy oz, carats — with UK stone explained

ECB reference when available, dated snapshot otherwise — 28 currencies, not a bank quote

Convert time between any two IANA time zones — DST handled automatically

Live current time in any two cities — time difference updated every second

Weekly timesheet — clock-in/out with break deductions, weekly pay estimate

Add or subtract hours and minutes — convert decimal hours to H:MM

12-hour AM/PM ↔ 24-hour military time — full reference table

Live countdown to any future date/event — days, hours, minutes, seconds

Road trip fuel cost — MPG (US/UK), L/100km — split by passengers

Appliance running cost daily/monthly/annually — country-specific rates

Convert MPG (US), MPG (UK), L/100km, km/L — explains gallon difference

Annual output, savings & payback — US ITC 30%, UK SEG, AU STC rebates

Solve speed/distance/time in mph, km/h, m/s, knots — speed limits by country

Bits, bytes, KB, MB, GB, TB — SI vs IEC binary (GiB vs GB) explained

Download/upload time from file size and connection speed — Mbps vs MB/s

Hours between two times, add/subtract hours & minutes

Trip fuel cost from MPG or L/100km — US, UK, Europe, Australia

Weighted grades — US letter, UK Honours, German, French scales

Punnett squares — monohybrid, dihybrid, ABO blood types, X-linked traits

DNA → mRNA → protein with codon table & mutation explorer

Total area of multiple rooms in ft², m², yd² & acres + material cost — how floor area is measured worldwide

Cubic yards (US), cubic metres (UK/AU), bag counts for 60/80lb and 20/25kg bags

Gallons (US) or litres (UK/AU) — deducts doors & windows, any number of coats

Square feet, square metres & square yards with waste factor for any lay pattern

Square yards (US) vs linear metres of 4m roll (UK/AU) — includes pattern repeat waste

Tiles & boxes from room area and tile size — inches (US) or centimetres (UK/AU)

Board feet (US/CA) or lineal metres (UK/AU) — explains nominal vs actual size

Cubic yards (US), cubic metres (UK/AU), and bag counts for 2 cu ft, 60L, 70L bags

Volume and weight for pea gravel, crushed stone, river rock — US tons & metric tonnes

Panels, posts & rails — US 8ft, UK 6ft, AU 1.8m standard panel sizes

Roofing squares (US/CA) or m² (UK/AU) with pitch factor — shingles & tiles

Cryptographically secure — follows NIST (US), NCSC (UK), ACSC (AU) guidelines

Words, chars, reading time, sentences — Twitter, SMS, LinkedIn platform limits

HEX ↔ RGB ↔ HSL ↔ HSV ↔ CMYK — web (RGB) vs print (CMYK) explained

CIDR network/broadcast/host range — RFC 1918 private ranges explained

Name compatibility % + the classic FLAMES game, plus how love traditions differ worldwide