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With numeric values in a gt table, we can transform those to values of bytes with human readable units. The fmt_bytes() function allows for the formatting of byte sizes to either of two common representations: (1) with decimal units (powers of 1000, examples being "kB" and "MB"), and (2) with binary units (powers of 1024, examples being "KiB" and "MiB").

It is assumed the input numeric values represent the number of bytes and automatic truncation of values will occur. The numeric values will be scaled to be in the range of 1 to <1000 and then decorated with the correct unit symbol according to the standard chosen. For more control over the formatting of byte sizes, we can use the following options:

  • decimals: choice of the number of decimal places, option to drop trailing zeros, and a choice of the decimal symbol

  • digit grouping separators: options to enable/disable digit separators and provide a choice of separator symbol

  • pattern: option to use a text pattern for decoration of the formatted values

  • locale-based formatting: providing a locale ID will result in number formatting specific to the chosen locale


  rows = everything(),
  standard = c("decimal", "binary"),
  decimals = 1,
  n_sigfig = NULL,
  drop_trailing_zeros = TRUE,
  drop_trailing_dec_mark = TRUE,
  use_seps = TRUE,
  pattern = "{x}",
  sep_mark = ",",
  dec_mark = ".",
  force_sign = FALSE,
  incl_space = TRUE,
  locale = NULL



A table object that is created using the gt() function.


The columns to format. Can either be a series of column names provided in c(), a vector of column indices, or a helper function focused on selections. The select helper functions are: starts_with(), ends_with(), contains(), matches(), one_of(), num_range(), and everything().


Optional rows to format. Providing everything() (the default) results in all rows in columns being formatted. Alternatively, we can supply a vector of row captions within c(), a vector of row indices, or a helper function focused on selections. The select helper functions are: starts_with(), ends_with(), contains(), matches(), one_of(), num_range(), and everything(). We can also use expressions to filter down to the rows we need (e.g., [colname_1] > 100 & [colname_2] < 50).


The way to express large byte sizes.


An option to specify the exact number of decimal places to use. The default number of decimal places is 1.


A option to format numbers to n significant figures. By default, this is NULL and thus number values will be formatted according to the number of decimal places set via decimals. If opting to format according to the rules of significant figures, n_sigfig must be a number greater than or equal to 1. Any values passed to the decimals and drop_trailing_zeros arguments will be ignored.


A logical value that allows for removal of trailing zeros (those redundant zeros after the decimal mark).


A logical value that determines whether decimal marks should always appear even if there are no decimal digits to display after formatting (e.g, 23 becomes 23.). The default for this is TRUE, which means that trailing decimal marks are not shown.


An option to use digit group separators. The type of digit group separator is set by sep_mark and overridden if a locale ID is provided to locale. This setting is TRUE by default.


A formatting pattern that allows for decoration of the formatted value. The value itself is represented by {x} and all other characters are taken to be string literals.


The mark to use as a separator between groups of digits (e.g., using sep_mark = "," with 1000 would result in a formatted value of 1,000).


The character to use as a decimal mark (e.g., using dec_mark = "," with 0.152 would result in a formatted value of 0,152).


Should the positive sign be shown for positive numbers (effectively showing a sign for all numbers except zero)? If so, use TRUE for this option. The default is FALSE, where only negative numbers will display a minus sign.


An option for whether to include a space between the value and the units. The default of TRUE uses a space character for separation.


An optional locale ID that can be used for formatting the value according the locale's rules. Examples include "en" for English (United States) and "fr" for French (France). The use of a valid locale ID will override any values provided in sep_mark and dec_mark. We can use the info_locales() function as a useful reference for all of the locales that are supported. Any locale value provided here will override any global locale setting performed in gt()'s own locale argument.


An object of class gt_tbl.

Targeting the values to be formatted

Targeting of values is done through columns and additionally by rows (if nothing is provided for rows then entire columns are selected). Conditional formatting is possible by providing a conditional expression to the rows argument. See the Arguments section for more information on this.


Use exibble to create a gt table. Format the num column to have byte sizes in the decimal standard.

exibble %>%
  dplyr::select(num) %>%
  gt() %>%
  fmt_bytes(columns = num)

This image of a table was generated from the first code example in the `fmt_bytes()` help file.

Create a similar table with the fmt_bytes() function, this time showing byte sizes as binary values.

exibble %>%
  dplyr::select(num) %>%
  gt() %>%
    columns = num,
    standard = "binary"

This image of a table was generated from the second code example in the `fmt_bytes()` help file.

Function ID