diff --git a/DESCRIPTION b/DESCRIPTION
index 020269b..aafaca1 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -19,9 +19,12 @@ Imports:
     dplyr,
     fs,
     glue,
+    janitor,
+    phsmethods,
     readr,
     rlang,
-    tibble
+    tibble,
+    tidyr
 Suggests: 
     testthat (>= 3.0.0)
 Config/testthat/edition: 3
diff --git a/NAMESPACE b/NAMESPACE
index afd9c7d..618fb58 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -2,6 +2,7 @@
 
 export(find_latest_file)
 export(get_hscp_locality)
+export(get_pop_est)
 export(get_simd_datazone)
 export(get_simd_postcode)
 export(get_spd)
diff --git a/R/find_latest_file.R b/R/find_latest_file.R
index bc1fae5..5f3ecab 100644
--- a/R/find_latest_file.R
+++ b/R/find_latest_file.R
@@ -12,8 +12,9 @@
 #' passed to [fs::dir_info()] to search for the file.
 #' @param selection_method Valid arguments are "modification_date"
 #' (the default) or "file_name".
+#' @param ... Additional arguments passed to [fs::dir_info()].
 #'
-#' @return the [fs::path()] to the file
+#' @return the [fs::path()] to the file.
 #' @export
 #'
 #' @examples
@@ -25,13 +26,15 @@
 #' }
 find_latest_file <- function(directory,
                              regexp,
-                             selection_method = "modification_date") {
+                             selection_method = "modification_date",
+                             ...) {
   if (selection_method == "modification_date") {
     latest_file <- fs::dir_info(
       path = directory,
       type = "file",
       regexp = regexp,
-      recurse = TRUE
+      recurse = TRUE,
+      ...
     ) |>
       dplyr::arrange(
         dplyr::desc(.data$birth_time),
diff --git a/R/get_pop_est.R b/R/get_pop_est.R
new file mode 100644
index 0000000..475b91d
--- /dev/null
+++ b/R/get_pop_est.R
@@ -0,0 +1,176 @@
+#' Get population estimates
+#'
+#' This function retrieves population estimates based on various parameters.
+#' It reads population data from a specified file and filters it based on the
+#' input parameters. The function also allows for grouping by age and pivoting
+#' the data for wider format.
+#' @param level The geographic level for which to retrieve population estimates.
+#' One of "datazone", "intzone", "hscp", "ca", or "hb".
+#' @param version The version of the population estimates to use (default: "latest").
+#' @param min_year,max_year (optional) The minimum and maximum years to include in the results.
+#' @param age_groups Logical, indicating whether to aggregate population estimates by age groups.
+#' If `TRUE`, the `phsmethods::create_age_groups` function is used.
+#' @param pivot_wider Optionally reshape the data into a wider format, summarising population counts by the specified columns.
+#'   Allowed values:
+#'   * `FALSE` (default): Do not pivot.
+#'   * `TRUE` or `"all"`: Pivot by both sex and age/age group.
+#'   * `"age"`: Pivot by age/age group only.
+#'   * `"age-only"`: Pivot by age/age group and aggregate to remove sex.
+#'   * `"sex"`: Pivot by sex only.
+#'   * `"sex-only"`: Pivot by sex group and aggregate to remove age/age group
+#' @param ... Additional arguments passed to [phsmethods::create_age_groups()].
+#'
+#' @return A tibble containing the filtered and possibly transformed population data.
+#'
+#' @note
+#' Depending on the values for `age_groups` and `pivot_wider`, the resulting
+#' columns in the returned tibble will vary. Refer to the examples below for
+#' illustration.
+#'
+#' @export
+#'
+#' @examples
+#' # Basic Usage: Datazone Population Estimates (no filtering)
+#' get_pop_est("datazone")
+#'
+#' # Filter by Year:
+#' get_pop_est("ca", min_year = 1995, max_year = 2020)
+#'
+#' # Age Groups: Health Board (HB) Population Estimates by Age Group
+#' get_pop_est("hb", age_groups = TRUE)
+#'
+#' # Age Groups with Custom Settings:
+#' # Aggregate into 5-year age groups, with an open-ended final group "85+"
+#' get_pop_est("hb", age_groups = TRUE, by = 5, to = 85)
+#'
+#' # Pivot Wider (All): CA Population Estimates, Reshaped by Sex and Age Group
+#' # The result will have columns for each combination of sex and age group,
+#' # e.g., "pop_f_0_4", "pop_m_5_9", etc.
+#' get_pop_est("ca", age_groups = TRUE, pivot_wider = "all")
+#'
+#' # Pivot Wider (Age Only): CA Population Estimates, Reshaped by Age Group Only
+#' # This is useful if you only need the total population for each age group, regardless of sex.
+#' get_pop_est("ca", age_groups = TRUE, pivot_wider = "age-only")
+#'
+#' # Combined Filtering, Age Groups, and Pivoting:
+#' # CA population from 2015-2020, aggregated by 10-year age groups, and pivoted by sex
+#' # The result will have columns for each sex ("pop_f", "pop_m") and a row per age group.
+#' get_pop_est("ca", min_year = 2015, max_year = 2020, age_groups = TRUE, by = 10, pivot_wider = "sex")
+get_pop_est <- function(
+    level = c("datazone", "intzone", "hscp", "ca", "hb"),
+    version = "latest",
+    min_year = NULL,
+    max_year = NULL,
+    age_groups = FALSE,
+    pivot_wider = FALSE,
+    ...) {
+  level <- rlang::arg_match(level)
+  if (!inherits(pivot_wider, "logical")) {
+    pivot_wider <- rlang::arg_match(
+      pivot_wider,
+      values = c("all", "age", "age-only", "sex", "sex-only")
+    )
+  }
+
+  ext <- "rds"
+  pop_dir <- fs::path(get_lookups_dir(), "Populations", "Estimates")
+
+  file_name_re <- paste0(level, "[0-9]{0,4}_pop_est_[0-9]{4}_[0-9]{4}\\.", ext)
+
+  pop_path <- find_latest_file(
+    directory = pop_dir,
+    regexp = file_name_re,
+    ignore.case = TRUE
+  )
+
+  pop_est <- read_file(pop_path)
+
+  # Validate year range and filter
+  if (!is.null(min_year) && !is.null(max_year) && min_year > max_year) {
+    cli::cli_abort(
+      "Invalid years: {.arg min_year} must not be greater than {.arg max_year}"
+    )
+  }
+
+  if (!is.null(min_year)) {
+    min_year_available <- min(pop_est$year)
+    if (min_year < min_year_available) {
+      cli::cli_abort(
+        "{.arg min_year} must be at least {min_year_available} when using the
+        {.file {fs::path_file(pop_path)}} file."
+      )
+    }
+    pop_est <- dplyr::filter(pop_est, .data$year >= min_year)
+  }
+
+  if (!is.null(max_year)) {
+    max_year_available <- max(pop_est$year)
+    if (max_year > max_year_available) {
+      cli::cli_abort(
+        "{.arg max_year} must be at most {max_year_available} when using the
+        {.file {fs::path_file(pop_path)}} file."
+      )
+    }
+    pop_est <- dplyr::filter(pop_est, .data$year <= max_year)
+  }
+
+  # Create age groups
+  if (age_groups) {
+    pop_est <- pop_est |>
+      dplyr::mutate(
+        age_group = phsmethods::create_age_groups(x = .data$age, ...),
+        .keep = "unused"
+      ) |>
+      dplyr::group_by(dplyr::across(!.data$pop)) |>
+      dplyr::summarise(pop = sum(.data$pop), .groups = "drop")
+  }
+
+  # Pivot data
+  if (pivot_wider %in% list(TRUE, "all")) {
+    pop_est <- pop_est |>
+      pivot_data(
+        id_cols = -"sex",
+        names_from = c("sex_name", dplyr::if_else(age_groups, "age_group", "age"))
+      )
+  } else if (pivot_wider == "sex") {
+    pop_est <- pop_est |>
+      pivot_data(
+        id_cols = c(-"sex", dplyr::if_else(age_groups, "age_group", "age")),
+        names_from = "sex_name"
+      )
+  } else if (pivot_wider == "sex-only") {
+    pop_est <- pop_est |>
+      pivot_data(
+        id_cols = c(-"sex", -dplyr::if_else(age_groups, "age_group", "age")),
+        names_from = "sex_name"
+      )
+  } else if (pivot_wider == "age") {
+    pop_est <- pop_est |>
+      pivot_data(
+        id_cols = c(-"sex", "sex_name"),
+        names_from = dplyr::if_else(age_groups, "age_group", "age")
+      )
+  } else if (pivot_wider == "age-only") {
+    pop_est <- pop_est |>
+      pivot_data(
+        id_cols = c(-"sex", -"sex_name"),
+        names_from = dplyr::if_else(age_groups, "age_group", "age")
+      )
+  }
+
+  return(pop_est)
+}
+
+
+# Helper function to pivot data
+pivot_data <- function(data, id_cols, names_from) {
+  tidyr::pivot_wider(
+    data,
+    id_cols = {{ id_cols }},
+    names_from = !!names_from,
+    values_from = "pop",
+    values_fn = sum,
+    names_prefix = "pop_",
+    names_repair = janitor::make_clean_names
+  )
+}
diff --git a/man/find_latest_file.Rd b/man/find_latest_file.Rd
index cd54324..44dabd9 100644
--- a/man/find_latest_file.Rd
+++ b/man/find_latest_file.Rd
@@ -4,7 +4,12 @@
 \alias{find_latest_file}
 \title{Find the latest version of a file}
 \usage{
-find_latest_file(directory, regexp, selection_method = "modification_date")
+find_latest_file(
+  directory,
+  regexp,
+  selection_method = "modification_date",
+  ...
+)
 }
 \arguments{
 \item{directory}{The directory in which to search.}
@@ -15,9 +20,11 @@ passed to \code{\link[fs:dir_ls]{fs::dir_info()}} to search for the file.}
 
 \item{selection_method}{Valid arguments are "modification_date"
 (the default) or "file_name".}
+
+\item{...}{Additional arguments passed to \code{\link[fs:dir_ls]{fs::dir_info()}}.}
 }
 \value{
-the \code{\link[fs:path]{fs::path()}} to the file
+the \code{\link[fs:path]{fs::path()}} to the file.
 }
 \description{
 This will return the latest created file matching
diff --git a/man/get_pop_est.Rd b/man/get_pop_est.Rd
new file mode 100644
index 0000000..d103fea
--- /dev/null
+++ b/man/get_pop_est.Rd
@@ -0,0 +1,82 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/get_pop_est.R
+\name{get_pop_est}
+\alias{get_pop_est}
+\title{Get population estimates}
+\usage{
+get_pop_est(
+  level = c("datazone", "intzone", "hscp", "ca", "hb"),
+  version = "latest",
+  min_year = NULL,
+  max_year = NULL,
+  age_groups = FALSE,
+  pivot_wider = FALSE,
+  ...
+)
+}
+\arguments{
+\item{level}{The geographic level for which to retrieve population estimates.
+One of "datazone", "intzone", "hscp", "ca", or "hb".}
+
+\item{version}{The version of the population estimates to use (default: "latest").}
+
+\item{min_year, max_year}{(optional) The minimum and maximum years to include in the results.}
+
+\item{age_groups}{Logical, indicating whether to aggregate population estimates by age groups.
+If \code{TRUE}, the \code{phsmethods::create_age_groups} function is used.}
+
+\item{pivot_wider}{Optionally reshape the data into a wider format, summarising population counts by the specified columns.
+Allowed values:
+\itemize{
+\item \code{FALSE} (default): Do not pivot.
+\item \code{TRUE} or \code{"all"}: Pivot by both sex and age/age group.
+\item \code{"age"}: Pivot by age/age group only.
+\item \code{"age-only"}: Pivot by age/age group and aggregate to remove sex.
+\item \code{"sex"}: Pivot by sex only.
+\item \code{"sex-only"}: Pivot by sex group and aggregate to remove age/age group
+}}
+
+\item{...}{Additional arguments passed to \code{\link[phsmethods:create_age_groups]{phsmethods::create_age_groups()}}.}
+}
+\value{
+A tibble containing the filtered and possibly transformed population data.
+}
+\description{
+This function retrieves population estimates based on various parameters.
+It reads population data from a specified file and filters it based on the
+input parameters. The function also allows for grouping by age and pivoting
+the data for wider format.
+}
+\note{
+Depending on the values for \code{age_groups} and \code{pivot_wider}, the resulting
+columns in the returned tibble will vary. Refer to the examples below for
+illustration.
+}
+\examples{
+# Basic Usage: Datazone Population Estimates (no filtering)
+get_pop_est("datazone")
+
+# Filter by Year:
+get_pop_est("ca", min_year = 1995, max_year = 2020)
+
+# Age Groups: Health Board (HB) Population Estimates by Age Group
+get_pop_est("hb", age_groups = TRUE)
+
+# Age Groups with Custom Settings:
+# Aggregate into 5-year age groups, with an open-ended final group "85+"
+get_pop_est("hb", age_groups = TRUE, by = 5, to = 85)
+
+# Pivot Wider (All): CA Population Estimates, Reshaped by Sex and Age Group
+# The result will have columns for each combination of sex and age group,
+# e.g., "pop_f_0_4", "pop_m_5_9", etc.
+get_pop_est("ca", age_groups = TRUE, pivot_wider = "all")
+
+# Pivot Wider (Age Only): CA Population Estimates, Reshaped by Age Group Only
+# This is useful if you only need the total population for each age group, regardless of sex.
+get_pop_est("ca", age_groups = TRUE, pivot_wider = "age-only")
+
+# Combined Filtering, Age Groups, and Pivoting:
+# CA population from 2015-2020, aggregated by 10-year age groups, and pivoted by sex
+# The result will have columns for each sex ("pop_f", "pop_m") and a row per age group.
+get_pop_est("ca", min_year = 2015, max_year = 2020, age_groups = TRUE, by = 10, pivot_wider = "sex")
+}
diff --git a/phslookups.Rproj b/phslookups.Rproj
index 4f837c0..4885b3e 100644
--- a/phslookups.Rproj
+++ b/phslookups.Rproj
@@ -21,6 +21,6 @@ PackageUseDevtools: Yes
 PackageInstallArgs: --no-multiarch --with-keep.source
 PackageRoxygenize: rd,collate,namespace
 
-UseNativePipeOperator: No
+UseNativePipeOperator: Yes
 
 SpellingDictionary: en_GB