diff --git a/sentry-ruby/lib/sentry/client.rb b/sentry-ruby/lib/sentry/client.rb
index 800668982..e1571e8c8 100644
--- a/sentry-ruby/lib/sentry/client.rb
+++ b/sentry-ruby/lib/sentry/client.rb
@@ -304,8 +304,13 @@ def send_envelope(envelope)
     rescue => e
       log_error("Envelope sending failed", e, debug: configuration.debug)
 
-      envelope.items.map(&:data_category).each do |data_category|
-        transport.record_lost_event(:network_error, data_category)
+      envelope.items.each do |item|
+        transport.record_lost_event(
+          :network_error,
+          item.data_category,
+          num: item.item_count,
+          num_bytes: item.lost_event_byte_size
+        )
       end
 
       raise
diff --git a/sentry-ruby/lib/sentry/envelope/item.rb b/sentry-ruby/lib/sentry/envelope/item.rb
index 3f6d5f9bb..4a03c8855 100644
--- a/sentry-ruby/lib/sentry/envelope/item.rb
+++ b/sentry-ruby/lib/sentry/envelope/item.rb
@@ -25,6 +25,13 @@ def self.data_category(type)
       end
     end
 
+    def self.byte_data_category(data_category)
+      case data_category
+      when "log_item" then "log_byte"
+      when "trace_metric" then "trace_metric_byte"
+      end
+    end
+
     def initialize(headers, payload)
       @headers = headers
       @payload = payload
@@ -33,6 +40,20 @@ def initialize(headers, payload)
       @size_limit = SIZE_LIMITS[type]
     end
 
+    def byte_data_category
+      self.class.byte_data_category(data_category)
+    end
+
+    def item_count
+      headers[:item_count] || 1
+    end
+
+    def lost_event_byte_size
+      return unless byte_data_category
+
+      (payload.is_a?(String) ? payload : JSON.generate(payload)).bytesize
+    end
+
     def to_s
       [JSON.generate(@headers), @payload.is_a?(String) ? @payload : JSON.generate(@payload)].join("\n")
     end
diff --git a/sentry-ruby/lib/sentry/telemetry_event_buffer.rb b/sentry-ruby/lib/sentry/telemetry_event_buffer.rb
index 1ced8e360..29f348af8 100644
--- a/sentry-ruby/lib/sentry/telemetry_event_buffer.rb
+++ b/sentry-ruby/lib/sentry/telemetry_event_buffer.rb
@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require "json"
 require "sentry/threaded_periodic_worker"
 require "sentry/envelope"
 
@@ -58,7 +59,11 @@ def add_item(item)
 
         if size >= @max_items_before_drop
           log_debug("[#{self.class}] exceeded max capacity, dropping event")
-          @client.transport.record_lost_event(:queue_overflow, @data_category)
+          @client.transport.record_lost_event(
+            :queue_overflow,
+            @data_category,
+            num_bytes: JSON.generate(item.to_h).bytesize
+          )
         else
           @pending_items << item
         end
@@ -92,6 +97,7 @@ def send_items
       )
 
       discarded_count = 0
+      discarded_bytes = 0
       envelope_items = []
 
       if @before_send
@@ -102,6 +108,7 @@ def send_items
             envelope_items << processed_item.to_h
           else
             discarded_count += 1
+            discarded_bytes += JSON.generate(item.to_h).bytesize
           end
         end
       else
@@ -109,7 +116,7 @@ def send_items
       end
 
       unless discarded_count.zero?
-        @client.transport.record_lost_event(:before_send, @data_category, num: discarded_count)
+        @client.transport.record_lost_event(:before_send, @data_category, num: discarded_count, num_bytes: discarded_bytes)
       end
 
       return if envelope_items.empty?
diff --git a/sentry-ruby/lib/sentry/transport.rb b/sentry-ruby/lib/sentry/transport.rb
index d799dc7e2..71bd2f878 100644
--- a/sentry-ruby/lib/sentry/transport.rb
+++ b/sentry-ruby/lib/sentry/transport.rb
@@ -64,7 +64,7 @@ def send_envelope(envelope)
       end
     rescue Sentry::SizeExceededError
       serialized_items&.each do |item|
-        record_lost_event(:send_error, item.data_category)
+        record_lost_event(:send_error, item.data_category, num: item.item_count, num_bytes: item.lost_event_byte_size)
       end
     end
 
@@ -167,11 +167,16 @@ def envelope_from_event(event)
       envelope
     end
 
-    def record_lost_event(reason, data_category, num: 1)
+    def record_lost_event(reason, data_category, num: 1, num_bytes: nil)
       return unless @send_client_reports
       return unless CLIENT_REPORT_REASONS.include?(reason)
 
       @discarded_events[[reason, data_category]] += num
+
+      return unless num_bytes
+
+      byte_category = Envelope::Item.byte_data_category(data_category)
+      @discarded_events[[reason, byte_category]] += num_bytes if byte_category
     end
 
     def flush
@@ -211,7 +216,13 @@ def reject_rate_limited_items(envelope)
       envelope.items.reject! do |item|
         if is_rate_limited?(item.data_category)
           log_debug("[Transport] Envelope item [#{item.type}] not sent: rate limiting")
-          record_lost_event(:ratelimit_backoff, item.data_category)
+
+          record_lost_event(
+            :ratelimit_backoff,
+            item.data_category,
+            num: item.item_count,
+            num_bytes: item.lost_event_byte_size
+          )
 
           true
         else
diff --git a/sentry-ruby/spec/sentry/envelope/item_spec.rb b/sentry-ruby/spec/sentry/envelope/item_spec.rb
index 9a46d8d33..0b5feed0d 100644
--- a/sentry-ruby/spec/sentry/envelope/item_spec.rb
+++ b/sentry-ruby/spec/sentry/envelope/item_spec.rb
@@ -21,4 +21,50 @@
       end
     end
   end
+
+  describe '.byte_data_category' do
+    [
+      ['log_item', 'log_byte'],
+      ['trace_metric', 'trace_metric_byte'],
+      ['error', nil],
+      ['transaction', nil],
+      ['default', nil]
+    ].each do |data_category, byte_category|
+      it "maps data category #{data_category} to byte category #{byte_category.inspect}" do
+        expect(described_class.byte_data_category(data_category)).to eq(byte_category)
+      end
+    end
+  end
+
+  describe '#item_count' do
+    it "returns the item_count header when present" do
+      item = described_class.new({ type: "log", item_count: 5 }, { items: [] })
+      expect(item.item_count).to eq(5)
+    end
+
+    it "defaults to 1 when the header is absent" do
+      item = described_class.new({ type: "event" }, {})
+      expect(item.item_count).to eq(1)
+    end
+  end
+
+  describe '#lost_event_byte_size' do
+    it "returns the serialized payload byte size for byte-tracked items" do
+      payload = { items: [{ body: "hello" }] }
+      item = described_class.new({ type: "log", item_count: 1 }, payload)
+      expect(item.lost_event_byte_size).to eq(JSON.generate(payload).bytesize)
+      expect(item.lost_event_byte_size).to be > 0
+    end
+
+    it "uses the payload as-is when it is already serialized" do
+      payload = JSON.generate({ items: [{ body: "hello" }] })
+      item = described_class.new({ type: "log", item_count: 1 }, payload)
+      expect(item.lost_event_byte_size).to eq(payload.bytesize)
+    end
+
+    it "returns nil for items without a byte category" do
+      item = described_class.new({ type: "event" }, { foo: "bar" })
+      expect(item.lost_event_byte_size).to be_nil
+    end
+  end
 end
diff --git a/sentry-ruby/spec/sentry/metrics_spec.rb b/sentry-ruby/spec/sentry/metrics_spec.rb
index fe9739793..433971f2d 100644
--- a/sentry-ruby/spec/sentry/metrics_spec.rb
+++ b/sentry-ruby/spec/sentry/metrics_spec.rb
@@ -313,7 +313,7 @@
 
           expect(sentry_metrics.count).to eq(1)
           expect(sentry_metrics.first[:name]).to eq("test.allowed")
-          expect(Sentry.get_current_client.transport).to have_recorded_lost_event(:before_send, 'trace_metric', num: 2)
+          expect(Sentry.get_current_client.transport).to have_recorded_lost_event(:before_send, 'trace_metric', num: 2, num_bytes: a_value > 0)
         end
       end
     end
diff --git a/sentry-ruby/spec/sentry/structured_logger_spec.rb b/sentry-ruby/spec/sentry/structured_logger_spec.rb
index 3b91640fd..4b4aa8023 100644
--- a/sentry-ruby/spec/sentry/structured_logger_spec.rb
+++ b/sentry-ruby/spec/sentry/structured_logger_spec.rb
@@ -241,6 +241,7 @@
           expect(sentry_logs.size).to be(1)
 
           expect(transport.discarded_events).to include([:before_send, "log_item"] => 2)
+          expect(transport.discarded_events[[:before_send, "log_byte"]]).to be > 0
         end
       end
     end
diff --git a/sentry-ruby/spec/sentry/transport_spec.rb b/sentry-ruby/spec/sentry/transport_spec.rb
index af4e1b5cb..a7cb90a41 100644
--- a/sentry-ruby/spec/sentry/transport_spec.rb
+++ b/sentry-ruby/spec/sentry/transport_spec.rb
@@ -214,6 +214,83 @@
       end
     end
 
+    context "byte-count client outcomes" do
+      let(:log_events) do
+        3.times.map do
+          Sentry::LogEvent.new(level: :info, body: "User has logged in!")
+        end
+      end
+
+      let(:metric_events) do
+        3.times.map do
+          Sentry::MetricEvent.new(name: "my.metric", type: "counter", value: 1)
+        end
+      end
+
+      let(:log_envelope) do
+        envelope = Sentry::Envelope.new
+        envelope.add_item(
+          { type: "log", item_count: log_events.size, content_type: "application/vnd.sentry.items.log+json" },
+          { items: log_events.map(&:to_h) }
+        )
+        envelope
+      end
+
+      let(:metric_envelope) do
+        envelope = Sentry::Envelope.new
+        envelope.add_item(
+          { type: "trace_metric", item_count: metric_events.size, content_type: "application/vnd.sentry.items.trace-metric+json" },
+          { items: metric_events.map(&:to_h) }
+        )
+        envelope
+      end
+
+      describe "#record_lost_event" do
+        it "fans out into the paired byte category" do
+          subject.record_lost_event(:ratelimit_backoff, "log_item", num: 3, num_bytes: 1243)
+
+          expect(subject.discarded_events[[:ratelimit_backoff, "log_item"]]).to eq(3)
+          expect(subject.discarded_events[[:ratelimit_backoff, "log_byte"]]).to eq(1243)
+        end
+
+        it "does not record a byte category for non-byte-tracked categories" do
+          subject.record_lost_event(:ratelimit_backoff, "error", num: 1, num_bytes: 1243)
+
+          expect(subject.discarded_events.keys).to contain_exactly([:ratelimit_backoff, "error"])
+        end
+
+        it "does not record bytes when num_bytes is nil" do
+          subject.record_lost_event(:ratelimit_backoff, "log_item")
+
+          expect(subject.discarded_events.keys).to contain_exactly([:ratelimit_backoff, "log_item"])
+        end
+      end
+
+      context "when a batched log item is rate limited" do
+        before { subject.rate_limits.merge!("log_item" => Time.now + 60) }
+
+        it "records log_item count and log_byte size" do
+          log_item = log_envelope.items.first
+          subject.send_envelope(log_envelope)
+
+          expect(subject.discarded_events[[:ratelimit_backoff, "log_item"]]).to eq(3)
+          expect(subject.discarded_events[[:ratelimit_backoff, "log_byte"]]).to eq(JSON.generate(log_item.payload).bytesize)
+        end
+      end
+
+      context "when a batched trace metric item is rate limited" do
+        before { subject.rate_limits.merge!("trace_metric" => Time.now + 60) }
+
+        it "records trace_metric count and trace_metric_byte size" do
+          metric_item = metric_envelope.items.first
+          subject.send_envelope(metric_envelope)
+
+          expect(subject.discarded_events[[:ratelimit_backoff, "trace_metric"]]).to eq(3)
+          expect(subject.discarded_events[[:ratelimit_backoff, "trace_metric_byte"]]).to eq(JSON.generate(metric_item.payload).bytesize)
+        end
+      end
+    end
+
     context "log events" do
       let(:log_events) do
         5.times.map do |i|
diff --git a/sentry-ruby/spec/spec_helper.rb b/sentry-ruby/spec/spec_helper.rb
index 6aaf34d4a..c2cc7a056 100644
--- a/sentry-ruby/spec/spec_helper.rb
+++ b/sentry-ruby/spec/spec_helper.rb
@@ -93,9 +93,16 @@
     reset_sentry_globals!
   end
 
-  RSpec::Matchers.define :have_recorded_lost_event do |reason, data_category, num: 1|
+  RSpec::Matchers.define :have_recorded_lost_event do |reason, data_category, num: 1, num_bytes: nil|
     match do |transport|
       expect(transport.discarded_events[[reason, data_category]]).to eq(num)
+
+      next true unless num_bytes
+
+      byte_category = Sentry::Envelope::Item.byte_data_category(data_category)
+      expect(transport.discarded_events[[reason, byte_category]]).to match(num_bytes)
+
+      true
     end
   end
 end
diff --git a/sentry-ruby/spec/support/shared_examples_for_telemetry_event_buffers.rb b/sentry-ruby/spec/support/shared_examples_for_telemetry_event_buffers.rb
index 576779723..e26286e16 100644
--- a/sentry-ruby/spec/support/shared_examples_for_telemetry_event_buffers.rb
+++ b/sentry-ruby/spec/support/shared_examples_for_telemetry_event_buffers.rb
@@ -109,7 +109,7 @@
     it "records lost event when dropping due to queue overflow" do
       max_items_before_drop.times { subject.add_item(event) }
 
-      expect(client.transport).to receive(:record_lost_event).with(:queue_overflow, subject.data_category)
+      expect(client.transport).to receive(:record_lost_event).with(:queue_overflow, subject.data_category, num_bytes: a_value > 0)
 
       subject.add_item(event)
     end