diff --git a/NAMESPACE b/NAMESPACE
index 5927555..aaa84f6 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -135,6 +135,8 @@ export(sum_by_colnames)
 export(sum_by_dimnames)
 export(sum_by_rownames)
 export(timeit)
+export(to_a1_col)
+export(to_r1c1_col)
 export(traverse)
 export(trim_ws)
 export(type)
diff --git a/R/excel.R b/R/excel.R
index b12fbc7..6670064 100644
--- a/R/excel.R
+++ b/R/excel.R
@@ -1,3 +1,68 @@
+#' To a R1C1 format column
+#'
+#' Convert a cell or column string from A1 to R1C1 format.
+#'
+#' @param x A string specifying a cell or a column
+#' @return A numeric
+#'
+#' @examples
+#' # convert a cell or column string from A1 to R1C1 format
+#' \donttest{
+#' to_r1c1_col("C33")
+#' to_r1c1_col("ABC")
+#' to_r1c1_col("ABC123")}
+#'
+#' @export
+to_r1c1_col <- function(x) {
+  tbl <- seq_along(LETTERS)
+  names(tbl) <- LETTERS
+  spl <- unlist(strsplit(get_pattern("[A-Z]+", x), split = "",
+                         perl = TRUE))
+  num <- tbl[spl]
+  dig <- rev(seq_along(num) - 1)
+  return(sum(num * 26^dig))
+}
+
+#' To a A1 format column
+#'
+#' Convert a cell or column numeric from R1C1 to A1 format.
+#'
+#' @param x A string specifying a cell or a column
+#' @return A string
+#'
+#' @examples
+#' # convert a cell or column numeric from R1C1 to A1 format.
+#' \donttest{
+#' to_a1_col(1)
+#' to_a1_col(3)
+#' to_a1_col(26)}
+#'
+#' @export
+to_a1_col <- function(x) {
+  tbl <- seq_along(LETTERS)
+  names(tbl) <- LETTERS
+  if (x <= 26) {
+    return(paste0(names(tbl[x]), collapse = ""))
+  }
+  quo_vec <- vector(mode = "integer")
+  rem_vec <- vector(mode = "integer")
+  i <- 1
+  while (x > 26) {
+    quo_vec[i] <- quo <- x%/%26
+    rem_vec[i] <- rem <- x%%26
+    x <- quo
+    i <- i + 1L
+  }
+  quo <- quo_vec[length(quo_vec)]
+  z <- c(quo, rev(rem_vec))
+  for (i in rev(2:length(z))) {
+    if (z[i] == 0) {
+      z[i] <- 26
+      z[i - 1] <- z[i - 1] - 1L
+    }
+  }
+  return(paste0(names(tbl[z]), collapse = ""))
+}
 
 write_data <- function(wb, sheet, data, rc = c(1L, 1L), rowNames = TRUE,
                        fontName = "Comic Sans MS", borderColour = "#000000",
diff --git a/man/to_a1_col.Rd b/man/to_a1_col.Rd
new file mode 100644
index 0000000..a6d775b
--- /dev/null
+++ b/man/to_a1_col.Rd
@@ -0,0 +1,25 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/excel.R
+\name{to_a1_col}
+\alias{to_a1_col}
+\title{To a A1 format column}
+\usage{
+to_a1_col(x)
+}
+\arguments{
+\item{x}{A string specifying a cell or a column}
+}
+\value{
+A string
+}
+\description{
+Convert a cell or column numeric from R1C1 to A1 format.
+}
+\examples{
+# convert a cell or column numeric from R1C1 to A1 format.
+\donttest{
+to_a1_col(1)
+to_a1_col(3)
+to_a1_col(26)}
+
+}
diff --git a/man/to_r1c1_col.Rd b/man/to_r1c1_col.Rd
new file mode 100644
index 0000000..bbe82ea
--- /dev/null
+++ b/man/to_r1c1_col.Rd
@@ -0,0 +1,25 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/excel.R
+\name{to_r1c1_col}
+\alias{to_r1c1_col}
+\title{To a R1C1 format column}
+\usage{
+to_r1c1_col(x)
+}
+\arguments{
+\item{x}{A string specifying a cell or a column}
+}
+\value{
+A numeric
+}
+\description{
+Convert a cell or column string from A1 to R1C1 format.
+}
+\examples{
+# convert a cell or column string from A1 to R1C1 format
+\donttest{
+to_r1c1_col("C33")
+to_r1c1_col("ABC")
+to_r1c1_col("ABC123")}
+
+}