diff --git a/common/command.cc b/common/command.cc
index 7f276193..c175cd27 100644
--- a/common/command.cc
+++ b/common/command.cc
@@ -173,6 +173,9 @@ po::options_description CommandHandler::getGeneralOptions()
     general.add_options()("router2-heatmap", po::value<std::string>(),
                           "prefix for router2 resource congestion heatmaps");
 
+    general.add_options()("report", po::value<std::string>(),
+                          "write timing and utilization report in JSON format to file");
+
     general.add_options()("placed-svg", po::value<std::string>(), "write render of placement to SVG file");
     general.add_options()("routed-svg", po::value<std::string>(), "write render of routing to SVG file");
 
@@ -424,6 +427,14 @@ int CommandHandler::executeMain(std::unique_ptr<Context> ctx)
         ctx->writeSDF(f, vm.count("sdf-cvc"));
     }
 
+    if (vm.count("report")) {
+        std::string filename = vm["report"].as<std::string>();
+        std::ofstream f(filename);
+        if (!f)
+            log_error("Failed to open report file '%s' for writing.\n", filename.c_str());
+        ctx->writeReport(f);
+    }
+
 #ifndef NO_PYTHON
     deinit_python();
 #endif
diff --git a/common/context.h b/common/context.h
index 4468d3dd..1175caee 100644
--- a/common/context.h
+++ b/common/context.h
@@ -76,6 +76,10 @@ struct Context : Arch, DeterministicRNG
 
     // --------------------------------------------------------------
 
+    // provided by report.cc
+    void writeReport(std::ostream &out) const;
+    // --------------------------------------------------------------
+
     uint32_t checksum() const;
 
     void check() const;
diff --git a/common/report.cc b/common/report.cc
new file mode 100644
index 00000000..4b3b2418
--- /dev/null
+++ b/common/report.cc
@@ -0,0 +1,68 @@
+/*
+ *  nextpnr -- Next Generation Place and Route
+ *
+ *  Copyright (C) 2021  gatecat <gatecat@ds0.me>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#include "json11.hpp"
+#include "nextpnr.h"
+
+NEXTPNR_NAMESPACE_BEGIN
+
+using namespace json11;
+
+namespace {
+dict<IdString, std::pair<int, int>> get_utilization(const Context *ctx)
+{
+    // Sort by Bel type
+    dict<IdString, std::pair<int, int>> result;
+    for (auto &cell : ctx->cells) {
+        result[ctx->getBelBucketName(ctx->getBelBucketForCellType(cell.second.get()->type))].first++;
+    }
+    for (auto bel : ctx->getBels()) {
+        if (!ctx->getBelHidden(bel)) {
+            result[ctx->getBelBucketName(ctx->getBelBucketForBel(bel))].second++;
+        }
+    }
+    return result;
+}
+} // namespace
+void Context::writeReport(std::ostream &out) const
+{
+    auto util = get_utilization(this);
+    dict<std::string, Json> util_json;
+    for (const auto &kv : util) {
+        util_json[kv.first.str(this)] = Json::object{
+                {"used", kv.second.first},
+                {"available", kv.second.second},
+        };
+    }
+    dict<std::string, Json> fmax_json;
+    for (const auto &kv : timing_result.clock_fmax) {
+        fmax_json[kv.first.str(this)] = Json::object{
+                {"achieved", kv.second.achieved},
+                {"constraint", kv.second.constraint},
+        };
+    }
+    out << Json(Json::object{
+                        {"utilization", util_json},
+                        {"fmax", fmax_json},
+                })
+                    .dump()
+        << std::endl;
+}
+
+NEXTPNR_NAMESPACE_END
diff --git a/docs/report.md b/docs/report.md
new file mode 100644
index 00000000..a766bb3d
--- /dev/null
+++ b/docs/report.md
@@ -0,0 +1,22 @@
+# JSON Reports
+
+nextpnr can write a JSON report using `--report` post-place-and-route for integration with other build systems. It contains information on post-pack utilization and maximum achieved frequency for each clock domain, and is of the following format:
+
+```
+{
+    "utilization": {
+        <beltype>: {
+            "used": <number of bels used in design>,
+            "available": <total number of bels available in device>
+        }, 
+        ...
+    },
+    "fmax": {
+        <clock domain>: {
+            "achieved": <computed Fmax of routed design for clock in MHz>,
+            "constraint": <constraint for clock in MHz>
+        },
+        ...
+    }
+}
+```