diff --git a/flatgfa/src/cli/cmds.rs b/flatgfa/src/cli/cmds.rs
index 3bf22cd4..388739f5 100644
--- a/flatgfa/src/cli/cmds.rs
+++ b/flatgfa/src/cli/cmds.rs
@@ -14,20 +14,40 @@ use std::io::Write;
 /// print the FlatGFA table of contents
 #[derive(FromArgs, PartialEq, Debug)]
 #[argh(subcommand, name = "toc")]
-pub struct Toc {}
-
-pub fn toc(gfa: &flatgfa::FlatGFA) {
-    eprintln!("header: {}", gfa.header.len());
-    eprintln!("segs: {}", gfa.segs.len());
-    eprintln!("paths: {}", gfa.paths.len());
-    eprintln!("links: {}", gfa.links.len());
-    eprintln!("steps: {}", gfa.steps.len());
-    eprintln!("seq_data: {}", gfa.seq_data.len());
-    eprintln!("overlaps: {}", gfa.overlaps.len());
-    eprintln!("alignment: {}", gfa.alignment.len());
-    eprintln!("name_data: {}", gfa.name_data.len());
-    eprintln!("optional_data: {}", gfa.optional_data.len());
-    eprintln!("line_order: {}", gfa.line_order.len());
+pub struct Toc {
+    /// show sizes in bytes instead of element counts
+    #[argh(switch, short = 'b')]
+    bytes: bool,
+}
+
+pub fn toc(gfa: &flatgfa::FlatGFA, args: Toc) {
+    if args.bytes {
+        // Show sizes in bytes.
+        println!("header: {}", gfa.header.size());
+        println!("segs: {}", gfa.segs.size());
+        println!("paths: {}", gfa.paths.size());
+        println!("links: {}", gfa.links.size());
+        println!("steps: {}", gfa.steps.size());
+        println!("seq_data: {}", gfa.seq_data.size());
+        println!("overlaps: {}", gfa.overlaps.size());
+        println!("alignment: {}", gfa.alignment.size());
+        println!("name_data: {}", gfa.name_data.size());
+        println!("optional_data: {}", gfa.optional_data.size());
+        println!("line_order: {}", gfa.line_order.size());
+    } else {
+        // Show element counts (which is what we record physically in the TOC).
+        println!("header: {}", gfa.header.len());
+        println!("segs: {}", gfa.segs.len());
+        println!("paths: {}", gfa.paths.len());
+        println!("links: {}", gfa.links.len());
+        println!("steps: {}", gfa.steps.len());
+        println!("seq_data: {}", gfa.seq_data.len());
+        println!("overlaps: {}", gfa.overlaps.len());
+        println!("alignment: {}", gfa.alignment.len());
+        println!("name_data: {}", gfa.name_data.len());
+        println!("optional_data: {}", gfa.optional_data.len());
+        println!("line_order: {}", gfa.line_order.len());
+    }
 }
 
 /// list the paths
diff --git a/flatgfa/src/cli/main.rs b/flatgfa/src/cli/main.rs
index 03ee8357..43ce5b64 100644
--- a/flatgfa/src/cli/main.rs
+++ b/flatgfa/src/cli/main.rs
@@ -111,8 +111,8 @@ fn main() -> Result<(), &'static str> {
     };
 
     match args.command {
-        Some(Command::Toc(_)) => {
-            cmds::toc(&gfa);
+        Some(Command::Toc(sub_args)) => {
+            cmds::toc(&gfa, sub_args);
         }
         Some(Command::Paths(_)) => {
             cmds::paths(&gfa);
diff --git a/flatgfa/src/pool.rs b/flatgfa/src/pool.rs
index 228545ba..a53c1309 100644
--- a/flatgfa/src/pool.rs
+++ b/flatgfa/src/pool.rs
@@ -278,6 +278,11 @@ impl<'a, T> Pool<'a, T> {
             .enumerate()
             .map(|(i, item)| (Id::new(i), item))
     }
+
+    /// Get the in-memory size of the pool in bytes.
+    pub fn size(&self) -> usize {
+        std::mem::size_of_val(self.0)
+    }
 }
 
 impl<T> Index<Id<T>> for Pool<'_, T> {