無料の計算機とユーティリティ

計算機とユーティリティについて

Absolutoolは日常的なタスク向けに21の計算機、タイマー、ユーティリティを提供しています。パーセンテージ計算機での素早い計算から、BMI計算機での健康チェックまで、各ツールはブラウザ内で直接、即座に結果を提供します。

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What This Category Covers

The "calculator" category here is broader than the name suggests, it groups together math, time, finance, productivity, and personal-data utilities that share one thing: a small input, an instant answer. The classic scientific calculator works with trigonometric functions, logarithms, and memory registers; the percentage calculator handles the four common forms (X% of Y, what % is X of Y, what's X% increase from Y, what % change between X and Y) without making you remember the order; the matrix calculator handles 4x4 multiplication and inversion for graphics and engineering work. Each one is a single page with a focused interface.

Time and date tools sit alongside: the age, date, and duration calculators cover the questions that always come up around contracts and renewals; the world clock tracks multiple time zones for remote teams; the Pomodoro timer and stopwatch are productivity classics. Financial tools include loan amortization, compound interest projection, tip and receipt-split helpers, and an invoice generator. Personal-data tools like the BMI calculator and the password set never send your inputs anywhere, an important detail when the numbers are medical or security-related. Utility generators round out the category: QR codes, barcodes, lorem ipsum, and a typing-speed test.

Financial Calculators and the Formulas Behind Them

The Loan Calculator on this site uses the standard amortization formula: M = P × r × (1+r)^n / ((1+r)^n − 1) where M is the monthly payment, P is the principal, r is the monthly interest rate (annual rate divided by 12), and n is the number of monthly payments. It also produces the full amortization schedule, the same table a bank gives you. The Compound Interest Calculator applies A = P(1 + r/n)^(nt) where A is the final amount, n is the compounding frequency per year, and t is years. You can sanity-check any commercial calculator against these by computing a single year by hand.

The Tip Calculator handles tax-inclusive and tax-exclusive cases (the difference matters in jurisdictions where tax is added at the register) and rounds to the local currency's smallest denomination. The Receipt Splitter divides the bill across multiple people with per-item or even-split modes and shows everyone's exact owed amount including tax and tip share. The Invoice Generator produces a printable invoice with line items, tax, totals, and your company info, useful for freelancers without dedicated accounting software. All financial tools run in the browser, so client account numbers, contract amounts, and tax figures never leave your device.

Time, Timers, and Productivity

The Pomodoro Timer implements Francesco Cirillo's 1980s technique: 25 minutes of focused work followed by 5 minutes of break, with a longer break every fourth cycle. Research from the University of California Irvine and elsewhere consistently finds that timeboxing helps recover from interruption faster than open-ended work sessions, and the audible alarm at the end of each session is the key behavioral lever. The Countdown Timer is the more flexible variant: set any duration, get an alarm at the end. The Stopwatch records elapsed time with lap markers, useful for sports training and process timing.

The World Clock tracks up to a dozen cities at once and highlights the working-hours overlap, useful for remote teams scheduling meetings across time zones. The Age Calculator shows exact years, months, days, hours, minutes, and seconds from a birth date, useful for milestone planning. The Date Calculator handles "what date is 90 days from now" and "how many days between these dates" questions that come up around contracts. The Duration Calculator sums multiple hour/minute/second values, useful for billing freelance work or planning a music playlist length. None of these require an account, none transmit your dates anywhere.

Why Personal-Data Calculators Should Stay Local

When you type your weight into a BMI calculator, your salary into a tax estimator, or your password into a strength checker, you're feeding a tool real data about yourself. On most online calculators, that data is sent to a server and may be logged for "analytics" or "improvements". Brokers, insurers, and ad networks have all been documented buying this kind of behavioral signal: even seemingly innocuous inputs (age and BMI together, for example) form a fingerprint that can be matched against other databases. Every personal-data calculator on this site processes your input in the browser tab and never transmits it. The numbers are yours and stay yours.

The Password Generator and Password Strength checker have the strongest privacy requirement of the group: any password sent to a server is, in principle, compromised. The version here generates passwords using your browser's cryptographically-secure random source (crypto.getRandomValues) and tests strength locally with zxcvbn, the open-source library originally written at Dropbox. The result is a strength score and a list of weaknesses you can fix; the password itself never leaves your machine. This matters most for the people most likely to use such tools, system administrators and engineers handling credentials for production infrastructure.

Frequently Asked Questions