diff --git a/tensorflow/lite/micro/simple_memory_allocator.cc b/tensorflow/lite/micro/simple_memory_allocator.cc
index 911e1e404f7..d55e7e87640 100644
--- a/tensorflow/lite/micro/simple_memory_allocator.cc
+++ b/tensorflow/lite/micro/simple_memory_allocator.cc
@@ -23,6 +23,20 @@ limitations under the License.
 
 namespace tflite {
 
+SimpleMemoryAllocator::SimpleMemoryAllocator(ErrorReporter* error_reporter,
+                                             uint8_t* buffer_head,
+                                             uint8_t* buffer_tail)
+    : error_reporter_(error_reporter),
+      buffer_head_(buffer_head),
+      buffer_tail_(buffer_tail),
+      head_(buffer_head),
+      tail_(buffer_tail) {}
+
+SimpleMemoryAllocator::SimpleMemoryAllocator(ErrorReporter* error_reporter,
+                                             uint8_t* buffer,
+                                             size_t buffer_size)
+    : SimpleMemoryAllocator(error_reporter, buffer, buffer + buffer_size) {}
+
 SimpleMemoryAllocator* CreateInPlaceSimpleMemoryAllocator(
     ErrorReporter* error_reporter, uint8_t* buffer, size_t buffer_size) {
   SimpleMemoryAllocator tmp =
@@ -64,4 +78,28 @@ uint8_t* SimpleMemoryAllocator::AllocateFromTail(size_t size,
   return aligned_result;
 }
 
+uint8_t* SimpleMemoryAllocator::GetHead() const { return head_; }
+
+uint8_t* SimpleMemoryAllocator::GetTail() const { return tail_; }
+
+size_t SimpleMemoryAllocator::GetHeadUsedBytes() const {
+  return head_ - buffer_head_;
+}
+
+size_t SimpleMemoryAllocator::GetTailUsedBytes() const {
+  return buffer_tail_ - tail_;
+}
+
+size_t SimpleMemoryAllocator::GetAvailableMemory() const {
+  return tail_ - head_;
+}
+
+size_t SimpleMemoryAllocator::GetUsedBytes() const {
+  return GetBufferSize() - GetAvailableMemory();
+}
+
+size_t SimpleMemoryAllocator::GetBufferSize() const {
+  return buffer_tail_ - buffer_head_;
+}
+
 }  // namespace tflite
diff --git a/tensorflow/lite/micro/simple_memory_allocator.h b/tensorflow/lite/micro/simple_memory_allocator.h
index 223ef8398a4..5be260f9ed2 100644
--- a/tensorflow/lite/micro/simple_memory_allocator.h
+++ b/tensorflow/lite/micro/simple_memory_allocator.h
@@ -29,15 +29,9 @@ namespace tflite {
 class SimpleMemoryAllocator {
  public:
   SimpleMemoryAllocator(ErrorReporter* error_reporter, uint8_t* buffer_head,
-                        uint8_t* buffer_tail)
-      : error_reporter_(error_reporter),
-        buffer_head_(buffer_head),
-        buffer_tail_(buffer_tail),
-        head_(buffer_head),
-        tail_(buffer_tail) {}
+                        uint8_t* buffer_tail);
   SimpleMemoryAllocator(ErrorReporter* error_reporter, uint8_t* buffer,
-                        size_t buffer_size)
-      : SimpleMemoryAllocator(error_reporter, buffer, buffer + buffer_size) {}
+                        size_t buffer_size);
 
   // Allocates memory starting at the head of the arena (lowest address and
   // moving upwards).
@@ -46,16 +40,17 @@ class SimpleMemoryAllocator {
   // moving downwards).
   uint8_t* AllocateFromTail(size_t size, size_t alignment);
 
-  uint8_t* GetHead() const { return head_; }
-  uint8_t* GetTail() const { return tail_; }
-  size_t GetAvailableMemory() const { return tail_ - head_; }
-  size_t GetUsedBytes() const { return GetBufferSize() - GetAvailableMemory(); }
+  uint8_t* GetHead() const;
+  uint8_t* GetTail() const;
 
-  size_t GetHeadUsedBytes() const { return head_ - buffer_head_; }
-  size_t GetTailUsedBytes() const { return buffer_tail_ - tail_; }
+  size_t GetHeadUsedBytes() const;
+  size_t GetTailUsedBytes() const;
+
+  size_t GetAvailableMemory() const;
+  size_t GetUsedBytes() const;
 
  private:
-  size_t GetBufferSize() const { return buffer_tail_ - buffer_head_; }
+  size_t GetBufferSize() const;
 
   ErrorReporter* error_reporter_;
   uint8_t* buffer_head_;