# All online calculators

- Gregorian calendar. Julian calendar. The calendar eras.
The calculator convers julian calendar date to gregorian calendar date taking in account the calendar era.

- H264 Maximum References Frames
H264 Maximum References Frames

- Hack
Hack the three-digit code

- Hartley's formula
Hartley's formula to determine the amount of information contained in a message with length n.

- Heat Index
This calculator calculates heat index (apparent temperature), which is used by US meteorologists to determine the human-perceived equivalent temperature, as how hot it would feel if the humidity were some other value in the shade.

- Height in old Russian system of measures
This calculator computes height expressed in old Russian measure system units: arshins and vershoks

- Hill cipher
This calculator uses Hill cipher to encrypt/decrypt a block of text

- Hip roof calculator
This calculator will help you estimate hip roof parameters, including rafters and roof area

- Histogram
Histogram generation according to input data. The number of groups is determined by the Sturgess formula, other formulas or set manually

- Histogram group number
Sturges formula and other methods of determining the number of groups in histogram generation

- How many circles of radius r fit in bigger circle of radius R
This calculator estimates how many circles of radius r can be placed inside another circle of radius R.

- How many days are there between two dates?
This is simple day calculator which determines number of days between two dates.

- How many hours between two days
This online calculator helps you to calculate how many hours (and minutes) between two week days, i.e., Friday at 7 a.m. until Sunday at 9 p.m.

- How many months are there between two dates?
This online calculator calculates how many months are there between two dates.

- How many weeks are between two dates
This calculator determines number of weeks between two given dates

- How many workdays between two dates?
The calculator evaluates number of working days and holidays for a period of time. The calculator based on the U.S. federal holidays table recognised in most states.

- HTML table to JSON array
Th calculator converts the html table code to JSON array with optional data transpose and compression. It also visualizes numeric data on chart.

- Huffman coding
This online calculator generates Huffman coding based on a set of symbols and their probabilities

- Humidification loads
This online calculator answers question "how to choose" humidifier, by calculating humidification requirements given initial and target relative humidity and building parameters

- Humindex
This calculator calculates Humindex, index used by Canadian meteorologists to describe how hot the weather feels to the average person, by combining the effect of heat and humidity.