Calculator Tools

A list of our Calculator tools. Nothing you enter is sent to a server; it is all processed in your browser.

• Hourly Wage Converter & Overtime Pay Calculator

  Converts between hourly, daily, monthly, and annual wages, and simulates overtime, holiday, and late-night premium pay.

• Consumption Tax & Discount Calculator

  Converts between tax-included and tax-excluded prices, and calculates the discounted price from a discount rate or amount.

• Ratio & Percentage Calculator

  Reduces a ratio to its simplest whole-number form, solves for a missing term in a proportion, and converts between a part, a whole, a percentage, and a rate of change.

• BMI Calculator

  Calculates your Body Mass Index from height and weight, shows the WHO weight category, and gives the healthy weight range for your height.

• Freelancer Take-Home Pay Calculator

  Estimates a Japanese freelancer's income tax, reconstruction surtax, and resident tax from annual revenue, expenses, and deductions, with a rough take-home pay figure.

• Mortgage Prepayment Comparison Calculator

  Compares the interest saved, term shortened, or monthly payment reduced by a lump-sum mortgage prepayment, for both the "shorten term" and "reduce payment" strategies.

• Investment Growth Simulator

  Solves for any one of initial investment, monthly contribution, annual return, or time horizon from the other three under compound interest, with a chart and year-by-year table, plus a sustainable monthly withdrawal estimate.

• JASSO Student Loan Repayment Simulator

  Estimates the monthly payment, total repayment, and total interest for a JASSO Type 2 (interest-bearing) student loan, comparing the fixed-rate and rate-review repayment methods.

• Unit Converter (Length, Weight, Area, Volume, Temperature, Data)

  Convert length, weight, area, volume, temperature, and data size, including metric, imperial, traditional Japanese units, and KB vs KiB.

• Split Bill Calculator (Rounding & Uneven Shares)

  Split a total among people with rounding up, down, or to the nearest unit, and let some people pay more. Shows the extra or shortfall.

• BMR & Calorie Calculator

  Estimate your basal metabolic rate and daily calorie needs from age, sex, height, weight, and activity level, with calorie targets for losing or gaining weight.

• Japan Salary Take-Home Pay Calculator

  Estimate annual and monthly take-home pay in Japan from gross salary after social insurance, income tax, and resident tax, using 2025-2026 rules.

• Furusato Nozei Donation Limit Calculator

  Estimate the furusato nozei (hometown tax) donation limit for a ¥2,000 out-of-pocket cost from your salary and deductions, using 2025-2026 rules.

• My Number & Corporate Number Validator

  Validates or calculates the check digit of a Japanese My Number (12 digits) or Corporate Number (13 digits, incl. the invoice registration number). Nothing is sent to a server.

• Electricity Cost Calculator (Watts to Monthly & Yearly Cost)

  Estimate what an appliance costs to run from its wattage, daily hours, and rate per kWh. See cost per hour, day, month, and year.

• Download Time Calculator (File Size & Internet Speed)

  Calculate how long a download takes from the file size and your connection speed in Mbps, Gbps, or MB/s, with a real-world speed factor.

• Statistics Calculator (Mean, Median, Standard Deviation)

  Paste numbers to get mean, median, mode, variance, and standard deviation at once, plus a T-score for any value.

• Break-Even Calculator (Units, Sales & Target Profit)

  Work out break-even units and sales from price, variable cost, and fixed costs, plus the volume needed for a target profit.

• Fuel Cost Calculator

  Calculate fuel cost and cost per km from distance, fuel economy and price, and split a road trip among passengers.

• Aspect Ratio Calculator

  Simplify a width and height to an aspect ratio, or find the missing side from a ratio and one dimension. Includes 16:9 and 4:3 presets.

• Roman Numeral Converter

  Convert numbers 1–3999 to Roman numerals and back. Non-standard forms like IIII are flagged with the standard form, with lowercase and Unicode (Ⅻ) output and a quick-reference table.

• Prime Factorization, GCD & LCM Calculator

  Factor an integer into primes, list its divisors with their count and sum, and check primality. Also finds the GCD and LCM of several integers, with BigInt support.

• Permutation & Combination Calculator

  Calculate nPr, nCr, factorials and repetition variants exactly, with every digit shown even for huge values.

• GPA Calculator

  Calculate GPA from course credits and grades. Supports 4.0, 4.3 and Japanese university scales.

• Screen Size Calculator

  Convert a screen diagonal in inches to width and height in cm, and get PPI, dot pitch and a viewing distance estimate. Works backwards from cm too.

• Due Date & Pregnancy Week Calculator

  Estimate your due date, current pregnancy week and month, and key milestones from your last period, ovulation date, or a known due date.

• Paid Leave Days Calculator (Japan)

  Calculate annual paid leave grant dates and days in Japan from your hire date and weekly schedule, including proportional grants.

• Running Pace Calculator

  Calculate running pace, speed, finish time and distance, plus race predictions and heart rate zones.

• Loan & Revolving Payment Calculator

  Estimate monthly payments, total interest and payoff time for amortizing, equal-principal and revolving credit, with a repayment schedule.

• Size Converter (Clothing, Shoes & Rings)

  Convert women’s and men’s clothing, shoe and ring sizes between Japan, US, EU and UK. A handy guide for overseas shopping.

• Invoice, Quotation, Receipt & Delivery Note Generator

  Create invoices, quotations, receipts and delivery notes in Japan’s qualified invoice layout and save them as PDF, with per-rate tax totals and rounding options

• Unit Price Comparator

  Compare products by price per 100 g, 100 ml or item. Handles 3+ products, pack counts and tax, and shows the cheapest and the gap.

• Savings Goal Calculator

  Enter two of target amount, time frame and monthly savings to solve the third. Handles a starting balance and 0% interest, with a yearly table.

• Rental Initial Cost Calculator

  Estimate upfront rental costs in Japan (deposit, key money, agent fee, prepaid rent) and a rent guide from income.

• Bonus Take-Home Pay Calculator (Japan)

  Estimate your net bonus in Japan after social insurance and withholding income tax, from the gross bonus and last month’s pay (2025 brackets).

• Japan Income Wall Checker (Take-Home Reversal)

  Check Japan’s income walls (¥1.06M, ¥1.3M, ¥1.6M) for part-timers and dependents and see where take-home pay drops. Estimate only.

• Unemployment Benefit Calculator (Japan)

  Estimate Japan's unemployment insurance basic allowance: daily amount, benefit days and waiting period by age, insured period and reason.

• Childcare Leave, Maternity & Sickness Benefit Calculator (Japan)

  Estimate Japan’s childcare leave benefit (67% / 50%), maternity allowance and sickness allowance from your pay and standard remuneration.

• Retirement Allowance Tax Calculator

  Estimate tax on a Japanese retirement allowance: retirement income deduction, half taxation, income tax and resident tax.

• Rental Property Yield Calculator

  Estimate gross yield, net yield (NOI) and cash flow after loan payments for a rental property.

• Macro (PFC) Calculator

  Calculate daily protein, fat, and carb grams from your calorie target and macro ratio. Estimate calories from BMR and activity.

• Sleep Calculator

  Work out your bedtime or wake-up time from 90-minute sleep cycles, with an adjustable time to fall asleep.

• Pet Age Calculator (Dog & Cat)

  Convert your dog's or cat's age to human years, with a chart by dog size.

• Cooking Unit Converter

  Convert tablespoons, teaspoons, cups, grams and ml for flour, sugar, butter, honey and more, with a weight chart.

• Recipe Scaler

  Scale an ingredient list to any number of servings. Handles fractions, ranges and units

• Wallpaper, Paint, Tile & Flooring Quantity Calculator

  Estimate rolls of wallpaper, cans of paint, and tiles or flooring boxes from room size, minus doors and windows, plus waste.

• A/B Test Significance & Sample Size Calculator

  Check if an A/B test result is significant (p-value, z-test, confidence interval) and estimate the sample size you need.

• Linear Regression & Correlation Calculator

  Fit a least-squares regression line to x,y data: slope, intercept, correlation r and R², with a scatter plot and predictions.

• Matrix Calculator

  Add, multiply, transpose and invert matrices up to 6x6 and find determinants, with exact fractions or decimals.

• Quadratic & Linear System Solver

  Solve quadratic equations and 2- or 3-variable linear systems with step-by-step working, including complex roots and no-solution cases.

• Area & Volume Calculator

  Find the area of circles, triangles and trapezoids and the volume of cylinders, cones, spheres and boxes, with formulas and steps.

• Function Grapher

  Plot y=f(x) graphs online. Overlay up to 6 functions, pan and zoom, switch degrees/radians and save as PNG.

• Scientific Calculator

  Online scientific calculator with trig, logs, roots, powers and factorials. Keyboard input, degrees/radians, history.

• Daily Proration Calculator

  Prorate monthly rent, salary or subscription fees by days or dates, with calendar, 30-day or 365-day basis and rounding options

• Luhn Checker & Card Brand Detector

  Validate card numbers with the Luhn algorithm and detect the brand by IIN. Includes public payment test numbers.

• ISBN & EAN-13 Check Digit Validator

  Validate or calculate ISBN-10, ISBN-13 and EAN/JAN check digits and convert ISBN-10 to ISBN-13.

• Print Size Converter

  Convert mm, pt, px and inches by DPI, with an A-series and B-series paper size chart

• Lat/Long Converter (DMS) & Distance Calculator

  Convert latitude and longitude between decimal degrees and DMS, and calculate distance, bearing and midpoint of two points with Haversine.

• Ohm's Law Calculator

  Find voltage, current, resistance or power from any two. Also series/parallel resistance and LED resistor values.

• Resistor Color Code Calculator

  Read 4-, 5- and 6-band resistor color codes or convert a resistance to bands, with tolerance and the nearest E series value.

• Withholding Tax Calculator for Fees

  Calculate Japanese withholding tax on freelance fees (10.21%, 20.42% above ¥1M), the amount transferred, and net-to-invoice reverse math.

• Stamp Duty Calculator (Contracts & Receipts)

  Look up the Japanese revenue stamp tax for contracts, receipts and bills by document type and amount, including the relief rates.

• Gift Tax Calculator (Japan, Calendar-Year)

  Estimate Japanese gift tax with the ¥1.1M basic deduction, special and general rate tables, and split calculation for mixed gifts.

• Depreciation Calculator (Japan, Straight-Line & Declining)

  Yearly depreciation from cost and useful life: straight-line and 200% declining balance, monthly proration, and Japan small-asset checks.

• Parcel Size Checker (Sum of Sides & Weight Class)

  Enter length, width, height and weight to see the Yamato, Yu-Pack and Sagawa size class and whether Nekopos, Yu-Packet or Letter Pack fits. Shows the limit exceeded.

• FX Calculator (Pips, Lot Size, Margin)

  Calculate forex profit and loss in pips and yen plus required margin from the pair, lots, leverage, direction, entry and exit rate.

• METs Calorie Calculator

  Calculates calories burned from METs, body weight, and time. Includes a METs table of common activities and totals several exercises.

• Histogram Maker & Frequency Table

  Make a frequency distribution table (relative and cumulative) and a histogram from pasted data. Set the bin width and save as PNG.

• Large Number Chart

  Idle-game number cheat sheet: compare commas, K/M/B/T suffixes and Japanese units (万・億・兆), and convert any value.