🧮 Calculators & Daily Life

Calculators & Daily Life

Quick everyday calculations

33 tools
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Choose by task

This category covers everyday estimates involving dates, money, units, pace, and health-related reference values. Accuracy depends on both the input and the assumptions: whether endpoints count, how tax and rounding work, and which formula is used. These tools support comparison and planning; they do not replace medical, tax, financial, or legal advice.

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All tools

🍻 Bill SplitterSplit the bill, with tips & rounding 📅 Date CalculatorDays between & age 📏 Unit ConverterLength, weight, temperature… ％ Percentage CalculatorPercent & ratio 🧾 Sales Tax Calculator (Japan)Tax-in / tax-out at 8% / 10% ⚖️ BMI CalculatorBMI from height & weight 📜 Japanese Era Converter & Year TableWestern ⇔ Reiwa/Heisei/Showa + table 🏦 Loan CalculatorMonthly payment & interest 💴 Wage ConverterHourly ⇔ monthly ⇔ yearly 📈 Compound Interest CalculatorFuture value with contributions 🏷️ Discount CalculatorSale price & amount saved ⏱️ Timer & StopwatchCountdown, stopwatch & pomodoro 🌏 World Clock & Time ZonesCurrent times & time-zone convert 🛒 Unit Price Comparison (per gram)Which is cheaper per gram or item 🏠 Tsubo / m² / Tatami ConverterConvert tsubo ⇔ m² ⇔ tatami 📅 Business Days Calculator (Japan)Count days excluding holidays 🎒 Japan School Year Calculator & TableGrade & graduation years, with table 🛍️ Marketplace Fee & Points CalculatorNet payout after fees & points 🍳 Recipe Scaler & Unit ConverterScale servings & cooking units 🤰 Pregnancy Due Date CalculatorDue date & gestational age ▭ Aspect Ratio CalculatorRatio, pixels & CSS aspect-ratio 🏃 Running Pace CalculatorPace, speed, distance & time 🔥 BMR & Calorie CalculatorBMR & TDEE (Mifflin-St Jeor) 🌡️ Heat Index & WBGT EstimatorHeat and humidity indices at once 🚗 Speed, Distance & TimeSolve speed × time × distance 🍚 Rice Cup & Water CalculatorJapanese cups ↔ ml & water 💱 Currency Converter (manual rate)Convert with a rate you enter 📐 Area & Volume CalculatorArea & volume of common shapes 🎎 Shichi-Go-San Year CalculatorWhen to celebrate 7-5-3 🕯️ Memorial Service Date CalculatorBuddhist memorial dates from a date of death 🎌 Japanese Public HolidaysHoliday list & long weekends by year 🌸 24 Solar Terms (Nijūshi Sekki)Dates of Japan's 24 seasonal points 📺 TV & Screen Size Calculator with TableInches ⇔ cm, plus a size table

Articles in this category

How Japan's Public Holidays Are Decided — Substitute Holidays and the Equinox Japanese holidays follow the Holiday Law, not a fixed table. We explain substitute and 'citizens' holidays with a computed list of the years they actually occur. The Pitfalls of Japanese Era Conversion — the Showa/Heisei/Reiwa Boundaries Japanese eras switch on a specific day, not a year. A table of era-change dates and boundary conversions clears up the mistakes forms often make. A '6-Tatami Room' Isn't One Size — Kyoma, Chukyoma, Edoma, Danchima Tatami come in four regional standards, so a '6-tatami' room can differ by over 10%. A computed m² comparison from real tatami dimensions clears the confusion. Why Copier Ratios Are 141% and 71%: A/B Paper Size Guide A4 to A3 is 141% and A3 to A4 is 71% because the A series fixes the aspect ratio at 1:root 2. Here are all the A- and B-series dimensions, how to compute any ratio yourself, and why Japan's B series differs from ISO B.

4 more: See all articles →

A reliable workflow

  1. Align units and assumptions such as inclusive dates and tax-inclusive prices.
  2. Use an example to check rounding and output format.
  3. Enter the real values and review unusual or extreme inputs.
  4. For contracts, filings, or health decisions, compare the result with current official information or a qualified professional.

Before you start

  • Tax rates, fees, holidays, and interest rates can change; check the page's review date and the latest official source.
  • Rounding below one unit can make an estimate differ from an invoice or provider calculation.
  • BMI, BMR, and due-date calculations are population-level or general estimates, not individual diagnoses.

Frequently asked questions

Can I use these results in an official filing or decision?
Use them for comparison and preliminary planning. For a tax filing, contract, medical decision, or legal procedure, rely on current official material, the provider's statement, and a suitably qualified professional.
Why does another calculator give a different result?
The formula, inclusion of start and end dates, activity factor, rounding rule, or data review date may differ. Compare the stated assumptions and calculation method rather than only the final number.