Skip to content
This page is also available in your language. Switch

Sync settings

Choose what your account keeps in step on every device where you are signed in.

  • My tools

    Always synced: the tools on your board, their order and size.

  • The windows open on your start page, including what you typed in them.

  • Every note in the notepad – on the notepad page, on your board and in windows.

  • Every list of website shortcuts – on the shortcuts page, on your board and in windows.

  • Every grid in the cover grid maker – on its page, on your board and in windows.

  • Every list of bookmarked organisations in the OIN lookup – on its page, on your board and in windows.

  • Keeps your pipeline and saved recipes on all your devices. Your files are never synced – only the steps and settings.

Turning something off removes it from your account straight away. Your devices keep their own copy.

Notifications

Tools that can tell you about something new while a Synsi tab is open, even when you are in another tab or app. Choose them for this browser.

This browser cannot show notifications from websites.
Notifications are blocked for this site. Allow them in your browser’s site settings (the icon left of the address), then switch them on here.

  • Says “New message” while a Synsi tab is open – never who wrote it or what.

Your choice is stored in this browser only. Notifications never show personal content such as a message or a number. They work while a Synsi tab is open; closed tabs get none.

Browse all tools →

Math & Statistics

A set of practical math and statistics calculators, organized into basic math, algebra, statistics and probability.

Basic Math

Percentage Calculator

Free percentage calculator: find X% of Y, what percent X is of Y, the percentage change between two numbers, or add and subtract a percentage.

Fraction Calculator

Add, subtract, multiply, divide or simplify fractions and see the exact result and decimal equivalent.

Ratio Calculator

Simplify a two-part ratio and calculate each part as a percentage of the total.

Average Calculator

Find the arithmetic mean of a list of numbers, together with their sum and count.

GCD and LCM Calculator

Find the greatest common divisor (GCD) and least common multiple (LCM) of two whole numbers.

Square Root Calculator

Find the principal square root of a non-negative number.

Exponent Calculator

Calculate a base raised to a power, including fractional and negative exponents.

Factorial Calculator

Calculate n factorial, the product of all positive integers up to n.

Algebra

Quadratic Equation Calculator

Solve a quadratic equation in the form ax² + bx + c = 0 and inspect its discriminant and roots.

Linear Equation Calculator

Solve a linear equation in the form ax + b = 0 for x.

Logarithm Calculator

Calculate a logarithm for any positive value and valid positive base other than one.

Exponent Calculator

Calculate a base raised to a power, including fractional and negative exponents.

Scientific Calculator

Evaluate common scientific functions including trigonometry, logarithms, powers, roots and reciprocals.

Statistics

Mean, Median and Mode Calculator

Calculate the mean, median, mode and count for a set of numbers.

Standard Deviation Calculator

Calculate the mean, variance and standard deviation of a data set using a population or sample formula.

Variance Calculator

Calculate population or sample variance and standard deviation from a list of observations.

Percentage Change Calculator

Calculate the percentage increase or decrease between an original value and a new value.

Z-Score Calculator

Convert a value to a z-score using its mean and standard deviation.

Confidence Interval Calculator

Estimate a confidence interval for a mean using a sample mean, standard deviation, sample size and confidence level.

Correlation Coefficient Calculator

Calculate Pearson’s correlation coefficient from paired x and y data.

Linear Regression Calculator

Fit a straight line to paired x and y observations and calculate slope, intercept and R-squared.

Range Calculator

Find the minimum, maximum and range of a list of numerical values.

P-Value Calculator

Estimate a one-tailed or two-tailed p-value from a z-score under the standard normal distribution.

Probability

Probability Calculator

Calculate the probability of an event from favorable outcomes and the total number of equally likely outcomes.

Permutation and Combination Calculator

Calculate arrangements where order matters (permutations) or selections where it does not (combinations).

Normal Distribution Calculator

Calculate the z-score, cumulative probability and probability density for a normal distribution.

Bayes' Theorem Calculator

Update a prior probability using a true-positive rate and false-positive rate to calculate a posterior probability.

Popular presets

Math calculators for study and everyday problem solving

Use the calculators above for arithmetic, fractions, ratios, equations, statistical summaries and probability. Each page explains the method and shows the values used in its calculation.

Basic math and algebra

Simplify fractions and ratios, calculate averages, find GCD and LCM, or work with roots, powers and factorials. Solve linear and quadratic equations and use the scientific calculator for common functions.

Statistics and probability

Summarize a data set with mean, median, mode, range, variance and standard deviation. Explore z-scores, confidence intervals, correlation, regression and normal probabilities. Probability, permutations, combinations and Bayes’ theorem cover common counting and conditional probability questions.

Statistical results depend on how data was collected and which assumptions apply. Correlation and regression describe relationships in the entered values and do not, by themselves, show causation.