All calculators
Percentages
- Percentage calculator
X% of Y, X as a percent of Y, and the whole from a part.
- Percentage increase calculator
Percent increase or decrease between two numbers, or add a percent to a number.
- Percentage difference calculator
Percent difference, percent change and percentage points side by side.
Money
- Compound interest calculator
What a sum grows to at a set rate, with APY and the balance year by year.
- Investment calculator
Future value of a balance with regular deposits or withdrawals.
- Pay raise calculator
New pay after a raise, or the percent raise, for every pay period.
Retirement
- Retirement calculator
What your savings could reach by retirement, and the monthly saving a goal needs.
- How long will my money last?
How many years savings cover a monthly withdrawal, plus the 4% rule.
- 401(k) calculator
Balance at retirement with your employer match and the current IRS limits.
- 403(b) calculator
For school, hospital and nonprofit staff, with the 15-year rule.
- 457(b) calculator
For government and nonprofit plans, with both kinds of catch-up.
- Roth IRA calculator
How much you can put in at your income, and what it could grow to.
- Contribution limits
401(k), 403(b), 457(b), SIMPLE and IRA limits from the IRS notice, for your age.
- RMD calculator
Required minimum distribution for your age, from the IRS table.
Dates and time
- Age calculator
Exact age in years, months and days, plus your next birthday.
- Date calculator
The date a number of days, weeks, months or years away, or the days between two dates.
Math and stats
- Decimal to fraction calculator
Decimal to fraction in lowest terms, and fractions or percents back to decimals.
- Final grade calculator
The score you need on your final exam, or the grade a final score gives you.
- Probability calculator
Chance of two events together, or of a number of successes in repeated tries.
- Standard deviation calculator
Sample or population standard deviation, variance, mean, median and mode, with every step.
More date, fraction and grade calculators are on the way.
Why a paper tape?
Accountants used adding machines with a paper roll for a reason: you can see every number you entered and catch a slip before it costs you. Most online calculators show only the last result. Here, each sum stays on the tape with its answer, so you can scan back over a column of figures, spot a typo and copy the final number when you're sure.
How the order of operations works
The calculator follows the standard order you learned in school, often remembered as PEMDAS:
- Parentheses (brackets) first
- Multiplication and division, from left to right
- Addition and subtraction, from left to right
So 10 − 4 ÷ 2 is 8, not 3. If you want the subtraction first, write (10 − 4) ÷ 2. A basic pocket calculator would give 3 here, because it works through keys one at a time without looking ahead.
Using the % key for tips, tax and discounts
The percent key works the way it does on most desk calculators, which makes everyday sums quick:
| Type | Result | Meaning |
|---|---|---|
| 86 + 20% | 103.2 | $86 bill plus a 20% tip |
| 45 + 7.25% | 48.2625 | Price plus 7.25% sales tax |
| 120 − 35% | 78 | $120 with 35% off |
| 2400 × 15% | 360 | 15% of 2,400 |
For anything more involved, such as finding a percentage of change or working back to a pre-tax price, use the dedicated percentage calculators.
Questions people ask
Does this calculator follow the order of operations?
Yes. Multiplication and division are done before addition and subtraction, and anything in brackets is done first. 2 + 3 × 4 is 14, while (2 + 3) × 4 is 20.
How does the % key work?
After + or −, a percentage means “percent of the number before it”, like on a desk calculator: 200 + 10% = 220 and 200 − 10% = 180. After × or ÷, it simply divides by 100, so 50 × 10% = 5.
Can I use my keyboard?
Yes. Type numbers and + − * / ( ) % directly. Press Enter for equals, Backspace to delete and Escape to clear.
Why does 0.1 + 0.2 give exactly 0.3 here?
Computers store most decimals as tiny approximations, which is why some apps show 0.30000000000000004. We round results to 12 significant digits, which removes that noise without affecting real answers.
Is my history saved?
Only on this page while it’s open. The tape keeps your recent calculations so you can check them, and it is cleared when you leave or refresh. Nothing is sent to a server.