diff --git a/src/root/storage.cpp b/src/root/storage.cpp
index 585cf25..eb255f7 100644
--- a/src/root/storage.cpp
+++ b/src/root/storage.cpp
@@ -281,8 +281,6 @@ void StorageManager::AddFrame(const vector<unsigned short>& frame) {
     frames.push(frame);
     frames_count++;
 
-    constexpr size_t max_frames = 100000;
-
     if (frames.size() >= max_frames) {
         throw std::runtime_error("Too many frames in queue");
     }
@@ -307,6 +305,10 @@ unsigned int StorageManager::GetNumberOfFramesInQueue() {
     return frames.size();
 }
 
+double StorageManager::GetQueueUsage() {
+    return GetNumberOfFramesInQueue() / (double) max_frames;
+}
+
 std::pair<unsigned short, std::array<unsigned short, MAX_POINTS>> Event::get_signal_id_data_pair(size_t index) const {
     unsigned short channel = signal_ids[index];
     std::array<unsigned short, MAX_POINTS> data{};
diff --git a/src/root/storage.h b/src/root/storage.h
index e56c1cc..ab522e6 100644
--- a/src/root/storage.h
+++ b/src/root/storage.h
@@ -114,6 +114,7 @@ class StorageManager {
     void AddFrame(const std::vector<unsigned short>& frame);
     std::vector<unsigned short> PopFrame();
     unsigned int GetNumberOfFramesInQueue();
+    double GetQueueUsage();
     unsigned int GetNumberOfFramesInserted() const;
 
 private:
@@ -125,6 +126,7 @@ class StorageManager {
     std::queue<std::vector<unsigned short>> frames;
     std::atomic<unsigned long long> frames_count = 0;
     std::mutex frames_mutex;
+    const size_t max_frames = 500000; // this should be about 2GB when full (depends on frame size)
 };
 
 } // namespace feminos_daq_storage