diff --git a/library/compiler-builtins/compiler-builtins/src/lib.rs b/library/compiler-builtins/compiler-builtins/src/lib.rs
index c993209699be..342427aca9c7 100644
--- a/library/compiler-builtins/compiler-builtins/src/lib.rs
+++ b/library/compiler-builtins/compiler-builtins/src/lib.rs
@@ -11,6 +11,7 @@
 #![feature(repr_simd)]
 #![feature(macro_metavar_expr_concat)]
 #![feature(rustc_attrs)]
+#![feature(float_bits_const)]
 #![cfg_attr(f16_enabled, feature(f16))]
 #![cfg_attr(f128_enabled, feature(f128))]
 #![no_builtins]
diff --git a/library/core/src/num/f128.rs b/library/core/src/num/f128.rs
index 4630fd729c6a..140b955259ab 100644
--- a/library/core/src/num/f128.rs
+++ b/library/core/src/num/f128.rs
@@ -154,6 +154,11 @@ impl f128 {
     #[unstable(feature = "f128", issue = "116909")]
     pub const RADIX: u32 = 2;
 
+    /// The size of this float type in bits.
+    // #[unstable(feature = "f128", issue = "116909")]
+    #[unstable(feature = "float_bits_const", issue = "151073")]
+    pub const BITS: u32 = 128;
+
     /// Number of significant digits in base 2.
     ///
     /// Note that the size of the mantissa in the bitwise representation is one
diff --git a/library/core/src/num/f16.rs b/library/core/src/num/f16.rs
index 21ba8f1f2828..463f07da91b2 100644
--- a/library/core/src/num/f16.rs
+++ b/library/core/src/num/f16.rs
@@ -148,6 +148,11 @@ impl f16 {
     #[unstable(feature = "f16", issue = "116909")]
     pub const RADIX: u32 = 2;
 
+    /// The size of this float type in bits.
+    // #[unstable(feature = "f16", issue = "116909")]
+    #[unstable(feature = "float_bits_const", issue = "151073")]
+    pub const BITS: u32 = 16;
+
     /// Number of significant digits in base 2.
     ///
     /// Note that the size of the mantissa in the bitwise representation is one
diff --git a/library/core/src/num/f32.rs b/library/core/src/num/f32.rs
index c4ec774f5956..be908cb3894b 100644
--- a/library/core/src/num/f32.rs
+++ b/library/core/src/num/f32.rs
@@ -398,6 +398,10 @@ impl f32 {
     #[stable(feature = "assoc_int_consts", since = "1.43.0")]
     pub const RADIX: u32 = 2;
 
+    /// The size of this float type in bits.
+    #[unstable(feature = "float_bits_const", issue = "151073")]
+    pub const BITS: u32 = 32;
+
     /// Number of significant digits in base 2.
     ///
     /// Note that the size of the mantissa in the bitwise representation is one
diff --git a/library/core/src/num/f64.rs b/library/core/src/num/f64.rs
index 0bb881323577..73b20a50ff8e 100644
--- a/library/core/src/num/f64.rs
+++ b/library/core/src/num/f64.rs
@@ -398,6 +398,10 @@ impl f64 {
     #[stable(feature = "assoc_int_consts", since = "1.43.0")]
     pub const RADIX: u32 = 2;
 
+    /// The size of this float type in bits.
+    #[unstable(feature = "float_bits_const", issue = "151073")]
+    pub const BITS: u32 = 64;
+
     /// Number of significant digits in base 2.
     ///
     /// Note that the size of the mantissa in the bitwise representation is one
diff --git a/src/tools/miri/tests/pass/float.rs b/src/tools/miri/tests/pass/float.rs
index a74a66d5455a..052c83d1aa31 100644
--- a/src/tools/miri/tests/pass/float.rs
+++ b/src/tools/miri/tests/pass/float.rs
@@ -353,7 +353,7 @@ fn assert_bidir_unrep(f: $fty, i: $ity, msg: &str) {
             assert_itof(i, f, msg);
         }
 
-        let fbits = <$fty>::BITS;
+        let fbits = <$fty as Float>::BITS;
         let fsig_bits = <$fty>::SIGNIFICAND_BITS;
         let ibits = <$ity>::BITS;
         let imax: $ity = <$ity>::MAX;
@@ -528,9 +528,9 @@ macro_rules! test_ftof {
         assert!((<$f1>::NAN as $f2).is_nan(), "{} -> {} nan", stringify!($f1), stringify!($f2));
 
         let min_sub_casted = <$f1>::from_bits(0x1) as $f2;
-        let min_neg_sub_casted = <$f1>::from_bits(0x1 | 1 << (<$f1>::BITS - 1)) as $f2;
+        let min_neg_sub_casted = <$f1>::from_bits(0x1 | 1 << (<$f1 as Float>::BITS - 1)) as $f2;
 
-        if <$f1>::BITS > <$f2>::BITS {
+        if <$f1 as Float>::BITS > <$f2 as Float>::BITS {
             assert_feq(<$f1>::MAX as $f2, <$f2>::INFINITY, "max -> inf");
             assert_feq(<$f1>::MIN as $f2, <$f2>::NEG_INFINITY, "max -> inf");
             assert_biteq(min_sub_casted, f2zero, "min subnormal -> 0.0");
diff --git a/src/tools/test-float-parse/src/traits.rs b/src/tools/test-float-parse/src/traits.rs
index 65a8721bfa5c..0cb44d297bfb 100644
--- a/src/tools/test-float-parse/src/traits.rs
+++ b/src/tools/test-float-parse/src/traits.rs
@@ -155,7 +155,7 @@ impl Float for $fty {
                 const BITS: u32 = <$ity>::BITS;
                 const MAN_BITS: u32 = Self::MANTISSA_DIGITS - 1;
                 const MAN_MASK: Self::Int = (Self::Int::ONE << Self::MAN_BITS) - Self::Int::ONE;
-                const SIGN_MASK: Self::Int = Self::Int::ONE << (Self::BITS-1);
+                const SIGN_MASK: Self::Int = Self::Int::ONE << (<Self as Float>::BITS-1);
                 fn from_bits(i: Self::Int) -> Self { Self::from_bits(i) }
                 fn to_bits(self) -> Self::Int { self.to_bits() }
                 fn constants() -> &'static Constants {