diff --git a/src/uucore/src/lib/features/format/num_format.rs b/src/uucore/src/lib/features/format/num_format.rs
index 0acec0598a1..fac733a2253 100644
--- a/src/uucore/src/lib/features/format/num_format.rs
+++ b/src/uucore/src/lib/features/format/num_format.rs
@@ -293,13 +293,7 @@ impl Formatter for Float {
 
         let precision = match precision {
             Some(CanAsterisk::Fixed(x)) => x,
-            None => {
-                if matches!(variant, FloatVariant::Shortest) {
-                    6
-                } else {
-                    0
-                }
-            }
+            None => 6, // Default float precision (C standard)
             Some(CanAsterisk::Asterisk) => return Err(FormatError::WrongSpecType),
         };
 
@@ -350,11 +344,16 @@ fn format_float_scientific(
     case: Case,
     force_decimal: ForceDecimal,
 ) -> String {
+    let exp_char = match case {
+        Case::Lowercase => 'e',
+        Case::Uppercase => 'E',
+    };
+
     if f == 0.0 {
         return if force_decimal == ForceDecimal::Yes && precision == 0 {
-            "0.e+00".into()
+            format!("0.{exp_char}+00")
         } else {
-            format!("{:.*}e+00", precision, 0.0)
+            format!("{:.*}{exp_char}+00", precision, 0.0)
         };
     }
 
@@ -375,11 +374,6 @@ fn format_float_scientific(
         ""
     };
 
-    let exp_char = match case {
-        Case::Lowercase => 'e',
-        Case::Uppercase => 'E',
-    };
-
     format!("{normalized:.precision$}{additional_dot}{exp_char}{exponent:+03}")
 }
 
@@ -582,6 +576,10 @@ mod test {
         assert_eq!(f(12.345_678_9), "1.234568e+01");
         assert_eq!(f(1_000_000.0), "1.000000e+06");
         assert_eq!(f(99_999_999.0), "1.000000e+08");
+
+        let f = |x| format_float_scientific(x, 6, Case::Uppercase, ForceDecimal::No);
+        assert_eq!(f(0.0), "0.000000E+00");
+        assert_eq!(f(123_456.789), "1.234568E+05");
     }
 
     #[test]
diff --git a/tests/by-util/test_seq.rs b/tests/by-util/test_seq.rs
index 0c708506f7e..1fae070f41e 100644
--- a/tests/by-util/test_seq.rs
+++ b/tests/by-util/test_seq.rs
@@ -709,7 +709,30 @@ fn test_format_option() {
 }
 
 #[test]
-#[ignore = "Need issue #2660 to be fixed"]
+fn test_format_option_default_precision() {
+    new_ucmd!()
+        .args(&["-f", "%f", "0", "0.7", "2"])
+        .succeeds()
+        .stdout_only("0.000000\n0.700000\n1.400000\n");
+}
+
+#[test]
+fn test_format_option_default_precision_short() {
+    new_ucmd!()
+        .args(&["-f", "%g", "0", "0.987654321", "2"])
+        .succeeds()
+        .stdout_only("0\n0.987654\n1.97531\n");
+}
+
+#[test]
+fn test_format_option_default_precision_scientific() {
+    new_ucmd!()
+        .args(&["-f", "%E", "0", "0.7", "2"])
+        .succeeds()
+        .stdout_only("0.000000E+00\n7.000000E-01\n1.400000E+00\n");
+}
+
+#[test]
 fn test_auto_precision() {
     new_ucmd!()
         .args(&["1", "0x1p-1", "2"])
@@ -718,7 +741,6 @@ fn test_auto_precision() {
 }
 
 #[test]
-#[ignore = "Need issue #3318 to be fixed"]
 fn test_undefined() {
     new_ucmd!()
         .args(&["1e-9223372036854775808"])