# All online calculators

- Days between dates. The historical version.
Calculates number of days between two dates taking in account the date of transition to Gregorian calendar.

- Days count in several date spans
The calculator gives total number of days in date span list. Each date span is defined by start date and end date. The calculator can exclude multiple date date span intersections.

- Deal profitability analysis
Deal profitability analysis after paying taxes (VAT and income tax)

- Degrees-minutes-seconds to decimal degrees conversion and vice versa.
This online calculator converts the value of an angle given in the form of the degrees-minutes-seconds to degrees, expressed in decimal fraction and back from decimal fraction to degrees-minutes-seconds.

- Density of oil
Recalculation of density of oil for different temperature and pressure values. Formulas are taken from Russia's GOST R 8.610-2004. "State system for ensuring the uniformity of measurements. Density of oil. The tables for recalculation" standard

- Derivative
It finds one variable function derivative. Step by step differentiation solution is also provided.

- Determinant of 3x3 matrices
This calculator calculates the determinant of 3x3 matrices

- Determinant of a matrix
This online calculator computes determinant of a matrix, using it's definition

- Determination of the baby's sex
It's unscientific, but it surprisingly works.

- Determining air humidity with psychrometric method
- Dew point
This calculator determines dew point from given temperature and relative humidity of air

- Digital image size in pixels and photo print size
This article is about relation between image size in pixels and photographic print size. First, it recommends photographic print size for given digital image dimensions in pixels. Second, it finds resulting pixels per inch value for printed digital image with known linear and pixel dimensions.

- Direct observation error analisys
Calculates error of direct measurements for given measured value series and confidence interval.

- Display aspect ratio and dimensions
This online calculator finds screen dimensions - height, width and area, given the diagonal value and aspect ratio.

- Distance across the surface vs distance through the Earth
This calculator calculates distance across the surface of the Earth and distance through the Earth for given two points, then compares them.

- Distance between two cities
Calculates the distance between the two cities. Uses the directory of geographical city coordinates for the calculation.

- Distance calculator
Calculates distance between two geographic coordinates using haversine formula.

- Distance through the Earth
This calculator calculates the distance from one point on the Earth to another point, going through the Earth, instead of going across the surface.

- Dollars to rubles and vice versa by Central Bank of Russia exchange rate
- Doppler Effect in sound
Calculation of frequency and wavelength change for a moving source