diff --git a/src/sha256/SHA256.h b/src/sha256/SHA256.h
index 504f249..4498e9d 100644
--- a/src/sha256/SHA256.h
+++ b/src/sha256/SHA256.h
@@ -30,6 +30,8 @@ namespace arduino { namespace sha256 {
     class SHA256 {
     public:
 
+        static constexpr uint32_t HASH_SIZE = SHA256_DIGEST_SIZE;
+
         inline void begin() {
             return arduino::sha256::begin(&_ctx);
         }