diff --git a/Userland/Utilities/cksum.cpp b/Userland/Utilities/cksum.cpp
index 4710c9ab8d..b432af7973 100644
--- a/Userland/Utilities/cksum.cpp
+++ b/Userland/Utilities/cksum.cpp
@@ -41,18 +41,39 @@ int main(int argc, char** argv)
 
     bool fail = false;
     for (auto& path : paths) {
-        auto file = Core::File::construct((StringView(path) == "-") ? "/dev/stdin" : path);
+        auto filepath = (StringView(path) == "-") ? "/dev/stdin" : path;
+        auto file = Core::File::construct(filepath);
         if (!file->open(Core::OpenMode::ReadOnly)) {
             warnln("{}: {}: {}", argv[0], path, file->error_string());
             fail = true;
             continue;
         }
-        auto file_buffer = file->read_all();
-        auto bytes = file_buffer.bytes().size();
+        struct stat st;
+        if (fstat(file->fd(), &st) < 0) {
+            warnln("{}: Failed to fstat {}: {}", argv[0], filepath, strerror(errno));
+            fail = true;
+            continue;
+        }
         if (algorithm == "crc32") {
-            outln("{} {} {}", Crypto::Checksum::CRC32 { file_buffer.bytes() }.digest(), bytes, path);
+            Crypto::Checksum::CRC32 crc32;
+            while (!file->eof() && !file->has_error())
+                crc32.update(file->read(PAGE_SIZE));
+            if (file->has_error()) {
+                warnln("Failed to read {}: {}", filepath, file->error_string());
+                fail = true;
+                continue;
+            }
+            outln("{} {} {}", crc32.digest(), st.st_size, path);
         } else if (algorithm == "adler32") {
-            outln("{} {} {}", Crypto::Checksum::Adler32 { file_buffer.bytes() }.digest(), bytes, path);
+            Crypto::Checksum::Adler32 adler32;
+            while (!file->eof() && !file->has_error())
+                adler32.update(file->read(PAGE_SIZE));
+            if (file->has_error()) {
+                warnln("Failed to read {}: {}", filepath, file->error_string());
+                fail = true;
+                continue;
+            }
+            outln("{} {} {}", adler32.digest(), st.st_size, path);
         } else {
             warnln("{}: Unknown checksum algorithm: {}", argv[0], algorithm);
             exit(1);