diff --git a/src/uu/numfmt/locales/en-US.ftl b/src/uu/numfmt/locales/en-US.ftl
index d718e368af2..4e5faf56e7f 100644
--- a/src/uu/numfmt/locales/en-US.ftl
+++ b/src/uu/numfmt/locales/en-US.ftl
@@ -36,6 +36,7 @@ numfmt-after-help = UNIT options:
   Optional precision (%.1f) will override the input determined precision.
 
 # Help messages
+numfmt-help-debug = print warnings about invalid input
 numfmt-help-delimiter = use X instead of whitespace for field delimiter
 numfmt-help-field = replace the numbers in these input fields; see FIELDS below
 numfmt-help-format = use printf style floating-point FORMAT; see FORMAT below for details
@@ -74,3 +75,7 @@ numfmt-error-invalid-format-width-overflow = invalid format '{ $format }' (width
 numfmt-error-invalid-precision = invalid precision in format '{ $format }'
 numfmt-error-format-too-many-percent = format '{ $format }' has too many % directives
 numfmt-error-unknown-invalid-mode = Unknown invalid mode: { $mode }
+
+# Debug messages
+numfmt-debug-no-conversion = no conversion option specified
+numfmt-debug-header-ignored = --header ignored with command-line input
diff --git a/src/uu/numfmt/src/numfmt.rs b/src/uu/numfmt/src/numfmt.rs
index d5ce81138e7..80528dbd4c5 100644
--- a/src/uu/numfmt/src/numfmt.rs
+++ b/src/uu/numfmt/src/numfmt.rs
@@ -262,6 +262,8 @@ fn parse_options(args: &ArgMatches) -> Result<NumfmtOptions> {
 
     let zero_terminated = args.get_flag(ZERO_TERMINATED);
 
+    let debug = args.get_flag(DEBUG);
+
     Ok(NumfmtOptions {
         transform,
         padding,
@@ -274,15 +276,35 @@ fn parse_options(args: &ArgMatches) -> Result<NumfmtOptions> {
         format,
         invalid,
         zero_terminated,
+        debug,
     })
 }
 
+fn print_debug_warnings(options: &NumfmtOptions, matches: &ArgMatches) {
+    // Warn if no conversion option is specified
+    if options.transform.from == Unit::None
+        && options.transform.to == Unit::None
+        && options.padding == 0
+    {
+        show_error!("{}", translate!("numfmt-debug-no-conversion"));
+    }
+
+    // Warn if --header is used with command-line input
+    if options.header > 0 && matches.get_many::<OsString>(NUMBER).is_some() {
+        show_error!("{}", translate!("numfmt-debug-header-ignored"));
+    }
+}
+
 #[uucore::main]
 pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     let matches = uucore::clap_localization::handle_clap_result(uu_app(), args)?;
 
     let options = parse_options(&matches).map_err(NumfmtError::IllegalArgument)?;
 
+    if options.debug {
+        print_debug_warnings(&options, &matches);
+    }
+
     let result = match matches.get_many::<OsString>(NUMBER) {
         Some(values) => {
             let byte_args: Vec<&[u8]> = values
@@ -316,6 +338,12 @@ pub fn uu_app() -> Command {
         .override_usage(format_usage(&translate!("numfmt-usage")))
         .allow_negative_numbers(true)
         .infer_long_args(true)
+        .arg(
+            Arg::new(DEBUG)
+                .long(DEBUG)
+                .help(translate!("numfmt-help-debug"))
+                .action(ArgAction::SetTrue),
+        )
         .arg(
             Arg::new(DELIMITER)
                 .short('d')
@@ -466,6 +494,7 @@ mod tests {
             format: FormatOptions::default(),
             invalid: InvalidModes::Abort,
             zero_terminated: false,
+            debug: false,
         }
     }
 
diff --git a/src/uu/numfmt/src/options.rs b/src/uu/numfmt/src/options.rs
index a8d16bda9f6..fedcd19c9e3 100644
--- a/src/uu/numfmt/src/options.rs
+++ b/src/uu/numfmt/src/options.rs
@@ -8,6 +8,7 @@ use crate::units::Unit;
 use uucore::ranges::Range;
 use uucore::translate;
 
+pub const DEBUG: &str = "debug";
 pub const DELIMITER: &str = "delimiter";
 pub const FIELD: &str = "field";
 pub const FIELD_DEFAULT: &str = "1";
@@ -57,6 +58,7 @@ pub struct NumfmtOptions {
     pub format: FormatOptions,
     pub invalid: InvalidModes,
     pub zero_terminated: bool,
+    pub debug: bool,
 }
 
 #[derive(Clone, Copy)]
diff --git a/tests/by-util/test_numfmt.rs b/tests/by-util/test_numfmt.rs
index f79c760061d..44d3b6a057f 100644
--- a/tests/by-util/test_numfmt.rs
+++ b/tests/by-util/test_numfmt.rs
@@ -1181,3 +1181,23 @@ fn test_unit_separator() {
         new_ucmd!().args(args).succeeds().stdout_only(expected);
     }
 }
+
+#[test]
+fn test_debug_warnings() {
+    new_ucmd!()
+        .args(&["--debug", "4096"])
+        .succeeds()
+        .stdout_is("4096\n")
+        .stderr_is("numfmt: no conversion option specified\n");
+
+    new_ucmd!()
+        .args(&["--debug", "--padding=10", "4096"])
+        .succeeds()
+        .stdout_only("      4096\n");
+
+    new_ucmd!()
+        .args(&["--debug", "--header", "--to=iec", "4096"])
+        .succeeds()
+        .stdout_is("4.0K\n")
+        .stderr_is("numfmt: --header ignored with command-line input\n");
+}