🧮 Lots Of Calcs 🧮

A collection of everyday and business calculators.

Calculator Categories

General All 6 →

Basic Calculator

Standard arithmetic with keyboard support.

Scientific Calculator

Trig, logs, powers and roots, with a DEG/RAD toggle.

Percentage Calculator

X% of Y, X as a % of Y, or the % change between two values.

Fraction Calculator

Add, subtract, multiply and divide fractions, with the working shown.

Decimal ↔ Fraction

Convert either way, including recurring decimals done exactly.

Number to Words

Numbers written out in British English, plus ordinal and cheque wording.

Business & Analysis All 7 →

Margin vs Markup

Cost + margin% or markup% → sell price, and back-solve either way.

YoY / MoM Growth

Feed in a monthly series, get month-on-month and year-on-year change.

Add or remove VAT, plus a progressive income tax band split.

A/B Test Significance

Control plus any number of variants → uplift, z-score and p-value for each.

Weighted Average

Values and weights → the weighted average, with each row's contribution.

Token prices, caching and batch discounts → what an LLM API really costs.

Marketplace Fees

eBay, Etsy and Amazon fees itemised → what you keep, and what to list at.

Savings & Investing All 9 →

Compound annual growth rate between a start and end value.

Compound Interest

Starting amount + annual return + years → what you'd end up with.

Goal + current savings + time frame → the monthly contribution you need.

Mortgage Overpayment

See the interest and years you'd save by overpaying your mortgage.

Loan / APR Repayment

Loan amount + APR + term → monthly payment, total interest and amortisation.

Debt Snowball vs Avalanche

Both strategies on your debts — interest, months and payoff order.

What platform and fund charges really cost over a long horizon.

HP or PCP with a balloon — monthly payments, interest and true total cost.

Multiple spending categories at different rates → what a card really pays.

Everyday All 9 →

Bill + tip% + people → tip amount and per-person total.

Discount Calculator

Original price + % off → final price, including stacked discounts.

🧑‍🤝‍🧑

Equal split with tip%, or an itemized uneven split per person.

Score out of total → % and letter grade, plus weighted averages.

Length, weight, temperature and volume conversions.

Height + weight → Body Mass Index and category.

Fuel Cost / MPG

Distance, fuel price and efficiency → trip cost.

EV Charging Cost

What a charge costs, including losses — plus the yearly saving against petrol.

Any two of distance, time and pace → the third, plus speed and splits.

Home & DIY All 5 →

Household Bill Splitter

Add everyone's contribution %, list the bills, and split the total fairly.

Electricity Running Cost

Appliance wattage and hours → what it costs to run per day, month and year.

Paint & Flooring Coverage

Room dimensions → how much paint or flooring you'll need.

BTU / Radiator Sizing

Room dimensions → the heat output you need, in BTU and watts.

Watts, Amps & Volts

Convert power, current and voltage — DC, single phase and three phase.

Betting & Odds All 6 →

Fractional, decimal and American odds → implied probability and payout.

Win and place parts of an each-way bet → total return and profit.

Matched Betting / Lay

Back and lay odds → lay stake, liability and the profit locked in.

Split a stake across selections so the return is the same whichever wins.

Multiple legs → combined odds, return and profit, with acca bonus.

Full Cover Bets

Trixie, Yankee, Lucky 15, Heinz and Goliath — with non-runners handled properly.

Other All 7 →

Birthday Calculator

Your exact age, day of the week born, and days until your next birthday.

Date Difference

Years, months and days between two dates.

Time Zone Converter

Convert a date and time between two time zones, DST included.

Your dog's age in human years, adjusted for size, plus the epigenetic formula.

Your cat's age in human years, with lifestage and the ×7 myth debunked.

Roman Numeral Converter

Numbers to Roman numerals and back, with a breakdown and reference table.

Weight on Other Planets

What you'd weigh on the Moon, Mars, Jupiter, Saturn and the Sun.