Everyday Calculators
Free tools for percentages, dates, units, study, travel, passwords and text — the small maths that come up every week
The small maths of daily life
Most calculations people actually run are small: a discount at the till, the days until a deadline, a tip split five ways, how long a paint job will take. They are quick — but each has a rule that is easy to get wrong, and this category keeps one honest tool for each.
Numbers and percentages
- Percentage and Percentage Increase — the three percentage question types and the change between two values.
- Discount — sale prices with stacked discounts and tax.
- Tip & Bill Split — tips and per-person shares for any group size.
Dates, time and units
The Age Calculator counts years, months and days exactly; the Date Difference Calculator adds business days; the Time Calculator adds and subtracts durations; and the Unit Converter covers length, weight, temperature, area, volume and speed in both directions.
Study, travel, home and work tools
GPA weights courses by credit; Fuel Cost prices a trip by distance and consumption; Paint estimates litres and coats for a room; the Password Generator builds crypto-random passwords locally; and the Word Counter tracks words, characters and reading time as you type.
Everything runs in your browser — even offline once the page has loaded — and nothing you type is stored or sent.
日常生活里的小数学
人们真正会去算的，大多是小事：结账时的折扣、离截止日还有几天、五个人分账的小费、一面墙要刷多少漆。这些都很快——但每一件都有一条容易踩坑的规则，本分类为每件事配了一个老实的工具。
数字与百分比
- 百分比与百分比增长——三类百分比问题，以及两个数值之间的变化率。
- 折扣——叠加折扣加税后的到手价。
- 小费与分账——任意人数的小费与人均分摊。
日期、时间与单位
年龄计算器精确到年月日；日期间隔计算器还能数工作日；时间计算器做时长的加减；单位换算器覆盖长度、重量、温度、面积、体积与速度的双向换算。
学习、出行、居家与效率工具
GPA 计算器按学分加权课程；油费计算器按距离与油耗给行程计价；涂料计算器估算房间用漆量与涂刷遍数；密码生成器在本地生成加密级随机密码；字数统计器边打边统计词数、字符与阅读时长。
一切都在你的浏览器里运行——页面加载后即使离线也能用——输入的任何内容都不会被存储或发送。
Frequently Asked Questions
Do these tools work offline?
Yes. Every page is self-contained — once it has loaded, the calculation runs entirely in your browser with no server involved. If you lose connection mid-task, the tools keep working.
Is anything I type sent to a server?
No. There is no account system and no upload: inputs exist only in the page you are looking at, and disappear when you close it. The password generator and word counter are safe even for sensitive content.
What is the difference between the percentage and percentage-increase calculators?
The Percentage Calculator answers the three classic questions — X% of a number, one number as a percentage of another, and the change between two values. The Percentage Increase Calculator focuses on that change alone, with more detail about the rise or fall.
Last reviewed: October 5, 2026 · How we calculate · Sources: NIST, ISO 8601, NIST SP 800-63B
最近复核：2026 年 10 月 5 日 · 我们的计算方法 · 来源：NIST、ISO 8601、NIST SP 800-63B