# All online calculators

- Number of days in a year
- Number of flagstones for paving
This calculator will help you to estimates number of flagstones needed for paving

- Number of flagstones to units of area and vice versa
These calculators convert entered number of flagstones to area size and vice versa - calculate number of flagstones needed to cover entered ara size. Metric and imperial units are supported

- Number of working days between two dates (for Russia)
Calculator calculates the number of days between the two entered dates. Taking into account weekends, holidays and weekend shifts to work days, according to the published decrees of the government of the Russian Federation.

- Numerical integration
To calculate definite integral by the rectangle method, trapezoid method, Simpson method or other Newton-Cotes quadrature methods.

- Ohm's law
This calculator determines current by voltage and resistance using ohm law

- Old Russian (Byzantine) system of chronology
Old Russian calendar - years since world creation

- One-variable function graph
This online calculator plots one-variable function graph given function formula and range of variable

- Orthodox Easter date calculator
Using a modification of the Gauss algorithm to calculate Orthodox Easter date

- Parallel and perpendicular lines on a plane
This online calculator checks lines' slopes to see if they are parallel or perpendicular

- PBX channel number calculation
Calculates number of PBX telecommunications channels for given traffic load using Erlang B and Engset algorithms

- Pearson correlation coefficient
The calculation of the correlation coefficient of two random variables

- Percentage
This online calculator gives the percentage of the value. It also calculates the percentage of the sum (e.g. the income tax of the net salary) and the percentage of the difference (e.g. VAT of the gross amount).

- Petroleum product density
Petroleum product density conversion, according to GOST 3900-85

- Playfair cipher
This online calculator encrypts and decrypts a message given Playfair cipher keyword. Non-alphabetic symbols (digits, whitespaces, etc.) are ignored.

- Points of the compass
This online calculator outputs compass point given direction angle in degrees. Different compass roses (4, 8, 16, 32, 128-wind compass roses) are supported.

- Poisson Distribution. Probability density function, cumulative distribution function, mean and variance
This calculator calculates poisson distribution pdf, cdf, mean and variance for given parameters

- Polygon area
Online calculator which calculates area of a polygon given lengths of polygon sides and diagonals which split polygon to nonoverlapping triangles