Everyday math
Percentage calculator
X% of a number, what percent one number is of another, and the percent change between two numbers.
Answer: 30
Average calculator
Mean, median, range and standard deviation of a list of numbers.
Mean (average): 86.6
Weighted average calculator
An average where some numbers count more than others.
Weighted average: 83
Grade calculator
Your overall grade from scores and their weights, with the letter grade on a standard scale.
Overall grade: 82.9%
Percent error calculator
How far a measured or estimated value is from the true value, as a percentage, with the math shown.
Percent error: 2.14%
Ratio calculator
Solve A : B = C : ?, simplify a ratio to its smallest whole numbers, or split an amount in a ratio.
D: 1,080
Scientific
Statistics
Standard deviation calculator
Sample and population standard deviation, variance, mean and standard error of a list of numbers.
Sample standard deviation (s): 3.1015
Z-score calculator
How many standard deviations a value is from the mean, and the percentile it falls at in a normal distribution.
Z-score: 2
Normal distribution calculator
The probability that a normally distributed value falls below, above or between two values.
Between a and b: 77.45%
Confidence interval calculator
The margin of error and range for a sample mean at 80% to 99.9% confidence.
Confidence interval: 69.783–74.217
Sample size calculator
How many people to survey for a given margin of error and confidence level, with an optional population size.
Sample size needed: 385
Combinations & permutations calculator
How many ways to choose r items from n: combinations (order doesn’t matter), permutations (order matters), with or without repeats.
Combinations C(n, r): 2,598,960