# All online calculators

- Date plus days
This online calculator adds or subtracts given number of days to or from the given date.

- Date to timestamp converter
This calculator converts date to epoch timestamp in milliseconds, that is, milliseconds since standard epoch of 1/1/1970, as used, for example, in Javascript.

- Date weeks out or before
This online calculator adds or subtracts given number of weeks to or from a given date.

- Day of week by date
This online calculator outputs day of week for given date

- 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.

- Discount calculator
This online calculator finds the discount from the sale price and the usual price, the sale price from the discount and the usual price and the usual price from the sale price and the discount

- 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.