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Note that this help is available from within the calculator, just select Help from the main menu.

Basic Operation

Number Entry

The number keys to and decimal point are used to enter numbers. To enter a negative number, press after entering the number.

The key deletes the last digit entered and can be used to correct a number or exponent.

The key clears the display ready for a new calculation.


To enter a number with an exponent, press then enter the exponent using the number and keys. Note that the exponent key means 'times 10 to the power' and it is not necessary to enter the 'times 10' yourself. The maximum exponent which can be entered is 999.

For example, to enter 2.5x1012, press:

 →  2.5x1012

Secondary Functions

The key is used to access the secondary function of each key (displayed above the key in orange). While shift is active, 'SHIFT' will be shown on the display. Press again to cancel shift mode.

As an alternative to using shift, the secondary function of each key can also be accessed by holding down the key. This feature can be disabled in Settings.

Throughout this help, functions which require shift to access are shown in orange. The shift key itself is not shown.

Keyboard Support

External hardware keyboards are supported for value entry and calculations. Each calculator function is mapped to a single key. The keyboard is used as follows:

  • Use the digit keys, together with 'e' for exponent, to enter values.
  • Use '+', '-', '*' and '/' for the basic arithmetic operations.
  • Use 'Enter' or '=' for and the space bar for .
  • Use 'n' for the sign-change key (the '-' sign is only used for subtraction, not for entering negative values).
  • Use the arrow keys and 'Enter' to select values from dialogs.
  • Press '?' on the external keyboard to display the full key mapping (press '?' again or any other key to hide).

  • Display

    Number Format

    The display style can be selected between 7-segment, dot-matrix or standard font.

    Numbers can be formatted on the display using either a point or a comma as the decimal separator. Numbers can also be displayed with digit grouping, using either a comma/point or space to separate groups of digits. Note that grouping with a space is not supported with the 7-segment display style, due to the fixed layout of the digits.

    In decimal mode, the digit grouping can be selected between three-digit, four-digit or Indian grouping. For binary, hexadecimal or octal mode, numbers are always displayed in groups of four digits.

    These options can be changed in the settings, under 'Display Format'.

    Display Modes

    There are four display modes for calculation results. Use the key to cycle through the modes. The display will show 'FIX', 'SCI', 'ENG' or blank to indicate the current mode.

    Decimal Places

    To set the number of decimal places in FIX mode, or the number of significant digits in SCI or ENG modes, press . This will bring up a dialog to select the number of digits, together with the current value rounded appropriately. When the number of digits selected is fewer than the maximum available, the display will show the number of digits after the mode indicator e.g. FIX:5 or SCI:8.

    Normal mode

    The result is displayed as a normal floating point value if possible. If its magnitude is less than 0.0001 or larger than will fit in the display, then scientific notation is used (see SCI mode below). The number of decimal places cannot be adjusted in this mode.

    FIX mode (fixed decimal point)

    The result is displayed after rounding to the number of decimal places selected by . If there is not enough room, the result may be displayed with fewer decimal places.

    SCI mode (scientific notation)

    The result is displayed in the format A x 10B, with the mantissa (A) rounded to the number of significant digits selected by .

    ENG mode (engineering notation)

    This is the same as SCI mode, except that the exponent is set to a multiple of 3.


    The value used for calculations is the unrounded result stored internally, and not the rounded value shown on the display.

    History and Memory

    Result History

    Each time the key is pressed, the calculation result is added to a history list.

    The key presents a dialog showing the calculation result history, with the most recent results at the top. Select the required value to enter it into the calculator.

    Up to 50 results are stored. The history can be cleared using the button at the bottom of the dialog.

    Main Memory

    The main memory has four dedicated function keys:

  • stores the current display value into the main memory.
  • recalls the value stored in the main memory.
  • adds the current display value to the main memory.
  • subtracts the current display value from the main memory.
  • Whenever a non-zero value is stored in the main memory, the letter 'M' is shown on the display.

    The main memory can also be accessed via the and keys (see below).

    Additional Memories

    There are nine additional memories which can be accessed via the and keys. These keys show a dialog with the current values stored in the main memory 'M' and the additional memories '1' to '9'. Select the appropriate value to store or recall the memory value.

    Memory Reset

    The values stored in all the memories can be reset to zero using the button at the bottom of the store/recall dialog.

    Unit Conversion

    How to Convert

    The current display value can be converted between different units using the key.

  • First, select the unit type from the list (distance, area, speed, time, etc).
  • Second, select the unit to convert from. Drag the list up/down to scroll if necessary.
  • The dialog will show the value converted to all appropriate units, with the original value highlighted in orange.
  • Select the required value to enter it into the calculator.
  • Press the back button at any time to go back to the previous step.
  • Zero Values

    For most conversions, an original value of 0.0 will be replaced by 1.0 as a convenience to avoid converting zero to zero. This does not apply to conversions which are not a simple ratio, e.g. temperature.


    The unit conversion dialog only displays values in decimal, the current radix mode (BIN, OCT or HEX) is ignored.

    Basic Functions

    Arithmetic Calculations

    These are entered exactly as written:

     →  75.

    Operations can be joined together:

     →  11.

    Multiplication and division have precedence over addition and subtraction and will be performed first:

     →  7.

    The parentheses keys can be used to override the normal precedence:

     →  9.

    There is no limit to the number of parentheses which can be entered.

    Percentage Calculations

  • What is 10% of 200?
  •  →  20.

  • What percentage of 36 is 9?
  •  →  25.

  • What is a 10% increase of 200?
  •  →  220.

  • What is a 20% decrease of 500?
  •  →  400.

  • What is the percentage change from 125 to 128?
  •  →  2.4

    Powers and Roots

  • Find 202
  •  →  400.

  • Find 63
  •  →  216.

  • Find the square root of 25
  •  →  5.

  • Find the cube root of 64
  •  →  4.

  • Find the 4th root of 81
  •  →  3.

    Note that rational exponents with negative bases are supported for small rational powers (denominators up to 99999).

  • Find -64 to the power 2/3.
  •  →  16.


  • Find 1 / 4 + 1 / 5
  •  →  0.45


  • Find 2 pi
  •  →  6.28318530718

  • Find 1 / e
  •  →  0.36787944117


    The modulo function calculates the remainder after division. Integer and non-integer numbers are supported. For negative numbers, the result has the same sign as the divisor.

  • Find remainder after dividing 25 by 7
  •  →  4.

  • Find remainder after dividing 8.5 by 2.6
  •  →  0.7

  • Find -8 modulo 5
  •  →  2.

  • Find 8 modulo -5
  •  →  -2.

    Repeat Calculations

    Repeat calculations can be performed without re-entering the value and function key, by pressing the operator twice. A 'K' is shown in the display to indicate that the repeat feature is active. For example:

     →  30.

    20 is now a constant for addition:

     →  80.

     →  50.

     →  70.

     →  90.

    Similarly for subtraction, multiplication and division:

     →  7.

     →  12.

     →  4.

     →  10.

     →  14.

     →  25.

     →  20.

    The auto-repeat mode is cancelled when another operator is pressed, or when or is pressed.

    It is also possible to enable the auto-repeat function permanently in the settings. In this case it is not necessary to press the operator twice, and there is no 'K' indicator in the display. This mode was the default operation in RealCalc prior to v2.0.

    Advanced Functions

    Logarithms and Exponentiation

  • Find ln(20.1)
  •  →  3.00071981507

  • Find log(316)
  •  →  2.49968708262

  • Find e3
  •  →  20.0855369232

  • Find 102.5
  •  →  316.227766017

    Trigonometric Functions

    For trigonometric functions, angles can be specified in degrees, radians or grads. The key cycles through the angle modes, and the display will show DEG, RAD or GRAD to indicate the current mode.

    The key also cycles through the angle modes, but also converts the current value in the display.

  • Find sin(30) (in DEG mode)
  •  →  0.5

  • Find tan(pi/4) (in RAD mode)
  •  →  1.

  • Find arcos(0.5) (in DEG mode)
  •  →  60.

  • Convert 180 degrees to radians
  •  →  3.14159265359

    Hyperbolic Functions

    For hyperbolic functions press the key before pressing , or . For inverse hyperbolic functions use in combination with . The 'HYP' indicator will appear in the display.

  • Find sinh(4)
  •  →  27.2899171971

  • Find arcosh(9)
  •  →  2.88727095036

    Factorials and Permutations

  • Find 10!
  •  →  3,628,800.

  • Find permutations of 3 items from 5
  •  →  60.

  • Find combinations of 3 items from 5
  •  →  10.

    Fractions & DMS


    Please note that Fractions and DMS are only available in RealCalc Plus.


    Fractions are entered using the key, and can be entered as either mixed or improper fractions. The results of calculations involving fractions will be displayed as fractions where appropriate, reduced to their lowest terms.

    Fraction Calculations

  • Find 2/3 + 3/4
  •  →  15/12

  • Find 11/8 - 21/2
  •  →  -11/8

  • Find 13/8 x 3/2
  •  →  21/16

    Fraction Conversion

    The key also converts between mixed fraction, improper fraction and decimal format.

  • Convert 3/8 to decimal, then back to fraction
  •  →  0.375

     →  3/8

  • Convert 2.55 to fraction, then to improper fraction, then to decimal
  •  →  211/20

     →  51/20

     →  2.55

  • If a decimal value cannot be converted to a fraction, then the key does nothing
  •  →  3.14159265359


    The following restrictions apply to fraction entry and results:

  • The maximum supported denominator is 99999.
  • The maximum number of digits in mixed fraction format is 10 or 12, depending on display mode.
  • Calculation results which do not meet these restrictions will be converted to decimal.

    Degrees, Minutes and Seconds (DMS)

    DMS values are entered using the key, and can be entered as either decimal degrees, whole degrees with decimal minutes, or whole degrees and minutes with decimal seconds.

    DMS Calculations

  • Find 2°30' + 1°45'20"
  •  →  4°15'20.00"

  • Find 2°3.5' + 125.3'
  •  →  4°08'48.00"

    DMS Conversion

    The key also converts between DMS and decimal format.

  • Convert 1.25 to DMS, then back to decimal.
  •  →  1°15'00.00"

     →  1.25

  • Convert 2°30 to decimal, then back to DMS.
  •  →  2.5

     →  2°30'00.00"


    The maximum value which can be displayed as DMS is 9999°59'59.9999". Calculation results outside this range will be converted to decimal.

    Binary, Octal and Hex

    Changing Mode

    These modes are set using the , and keys respectively. The key returns to the normal decimal mode. The current value on the display is truncated to an integer when switching modes (alternatively, rounding to integer is available as an option in the settings).

    Please note that these modes are disabled by default, and can be enabled in the settings.

    Number Range

    When in BIN, OCT or HEX modes, calculations are performed on signed integer values up to 12 digits. Non-integer results will be truncated.

    Negative values are represented in 2's, 8's or 16's complement notation.


     →  -1.

     →  1111,1111,1111.

     →  7777,7777,7777.


    Pressing the key negates the current value on the display:

     →  1111,1111,1001.

     →  111.

    Logical Operations

    The following bitwise logical operations are available (all examples in HEX mode):

  • - bitwise inversion
  •  →  FFFF,FFFF,FF8A.

  • - bitwise logical AND
  •  →  62.

  • - bitwise logical NAND
  •  →  FFFF,FFFF,FF9D.

  • - bitwise logical OR
  •  →  F7.

  • - bitwise logical NOR
  •  →  FFFF,FFFF,FF08.

  • - bitwise exclusive-OR
  •  →  95.

  • - bitwise exclusive-NOR
  •  →  FFFF,FFFF,FF6A.

    Shift & Rotate Functions

    The following bitwise shift and rotate functions are available (all examples in HEX mode):

  • - arithmetic shift left
  •  →  1,3CD0.

  • - arithmetic shift right
  •  →  FFFF,FFFF,FB0C.

  • - logical shift right
  •  →  1FFF,FFFF,FB0C.

  • - single-bit rotate left
  •  →  FFFF,FFFF,FE01.

  • - single-bit rotate right
  •  →  8000,0000,007F.

    History and Memory Dialogs

    When in BIN, OCT or HEX modes, the values in the history and memory dialogs are presented in the current mode. Values which cannot be converted to the current mode are shown as 'Error' and cannot be selected.

    RPN Mode

    RPN Mode

    RPN mode can be enabled in the Settings (select Calculator Type > RPN).

    In RPN mode, values are entered first, followed by the function key. Values are pushed onto a stack using the key. Functions take their arguments off the bottom of the stack, and push their result back onto the stack.

    RPN Styles

    Three styles of RPN behaviour are supported. The style can be selected in the Settings.

    1. Unlimited stack, no entry buffer.

    In this mode, new values are entered directly into the X register. It is not necessary to press the ENTER key before using the value in a calculation. If ENTER is pressed, the value is placed in both X and Y, and the value in X will be replaced by a new entry. The stack size is unlimited.

    The key drops the X value off the bottom of the stack, shifting the remainder of the stack down. If the stack becomes empty, a zero remains in the X register.

    The key swaps the values in the X and Y registers.

    This is the original RealCalc RPN behaviour (prior to version 2.0) and is the only style supported in the free version of RealCalc.

    2. Unlimited stack, with entry buffer.

    In this mode, new values are entered into a separate buffer (indicated by a right-arrow on the entry line). When ENTER is pressed, the value is placed in the first register only. It is not necessary to press the ENTER key before using the value in a calculation. The stack size is unlimited, and labeled 1,2,3 rather than X,Y,Z.

    The key drops the first value off the bottom of the stack, shifting the remainder of the stack down.

    The key swaps the values in the X and Y registers.

    (This mode is only available in RealCalc Plus).

    3. Four-level XYZT stack.

    In this mode, the stack size is fixed at four, labeled X,Y,Z,T. New values are entered directly into the X register. If ENTER is pressed, the value is placed in both X and Y, and the value in X will be replaced by a new entry.

    When the stack drops, the value in T is copied into Z (leaving T unchanged).

    The key rolls the stack down, moving the X value back into the T register.

    The key swaps the values in the X and Y registers.

    (This mode is only available in RealCalc Plus).

    Stack Operations

    The following additional functions are available in all RPN styles.

  • The key re-enters the value which was in the X register before the last operation.
  • The key opens a dialog which shows the contents of the stack.
  • The key reverses the last stack operation (any entry in progress is unaffected).
  • The key clears the stack.
  • RPN Operation

  • Functions which require a single argument, such as or , simply operate on X and replace it, in the same way as normal mode:
  •  →  X:      25.

  • Functions which require two arguments, such as or , take X and Y off the stack and put the result back:
  •  →  X:      6.

     →  X:      256.

    Note that the percent key calculates X% of Y, placing the result in X, but leaves Y unchanged.

  • Find (4+5)/(1+2)
  •  →  X:      3.

    If there are insufficient arguments on the stack for a particular operation, 'X?' and/or 'Y?' will be displayed for a short time.


    The size of the display can be changed to show the first one, two, three or four registers. Simply drag the display up or down to adjust, or alternatively this can be configured in the settings.

    Result History

    As there is no equals key, the result of every operation is added to the result history.


    Unit Conversions and Constants

    Please see this page for help on customizing the unit conversions and constants.


    Play Store Download and Licensing Issues

    Please see this page for help with common download and licensing issues.