diff --git a/Controller.cpp b/Controller.cpp
index 3cd51b5..0eb79f8 100644
--- a/Controller.cpp
+++ b/Controller.cpp
@@ -139,6 +139,20 @@ void Controller::startup()
         conns += connect(bitcoindmgr.get(), &BitcoinDMgr::allConnectionsLost, this, [this]{ stopTimer(mempoolLogTimer);});
     }
 
+    {
+        // set up periodid refresh of mempool fee histogram
+        constexpr const char *feeHistogramTimer = "feeHistogramTimer";
+        constexpr int feeHistogramTimerInterval = 10 * 1000;//500 * 1000; // 500 seconds
+        conns += connect(this, &Controller::upToDate, this, [this] {
+            callOnTimerSoon(feeHistogramTimerInterval, feeHistogramTimer, [this]{
+                refreshMempoolHistogram();
+                return true;
+            }, false, Qt::TimerType::VeryCoarseTimer);
+        });
+        // disable the timer if synchronizing and restart it later when up-to-date
+        conns += connect(this, &Controller::synchronizing, this, [this]{ stopTimer(feeHistogramTimer); });
+    }
+
     start();  // start our thread
 }
 
@@ -1172,6 +1186,23 @@ void Controller::process_DoUndoAndRetry()
     }
 }
 
+void Controller::refreshMempoolHistogram() const
+{
+    const auto t0 = Util::getTimeMicros();
+    Mempool::FeeHistogramVec hist;
+    {
+        auto [mempool, lock] = storage->mempool();
+        auto histtmp = mempool.calcCompactFeeHistogram();
+        hist.swap(histtmp);
+    }
+    const auto elapsed = Util::getTimeMicros() - t0;
+    Debug() << "Histogram: " << Util::Stringify(hist, [](const auto &val) {
+            auto & [feeRate, cumSize] = val;
+            return QString("(%1, %2)").arg(feeRate).arg(cumSize);
+    });
+    Debug() << "Refreshed mempool fee histogram in " << QString::number(elapsed/1e3, 'f', 4) << " msec";
+}
+
 // -- CtlTask
 CtlTask::CtlTask(Controller *ctl, const QString &name)
     : QObject(nullptr), ctl(ctl)
diff --git a/Controller.h b/Controller.h
index db2a668..a6c83d4 100644
--- a/Controller.h
+++ b/Controller.h
@@ -148,6 +148,9 @@ private:
 
     /// takes locks, prints to Log() every 30 seconds if there were changes
     void printMempoolStatusToLog() const;
+
+    /// called from a timer every 500 seconds -- takes locks, updates compact fee histogram
+    void refreshMempoolHistogram() const;
 };
 
 /// Abstract base class for our private internal tasks. Concrete implementations are in Controller.cpp.
diff --git a/Fulcrum.pro b/Fulcrum.pro
index 85e8205..9fd774e 100644
--- a/Fulcrum.pro
+++ b/Fulcrum.pro
@@ -146,6 +146,7 @@ SOURCES += \
     Common.cpp \
     Controller.cpp \
     Logger.cpp \
+    Mempool.cpp \
     main.cpp \
     Merkle.cpp \
     Mixins.cpp \
diff --git a/Mempool.cpp b/Mempool.cpp
new file mode 100644
index 0000000..34a15a3
--- /dev/null
+++ b/Mempool.cpp
@@ -0,0 +1,35 @@
+#include "Mempool.h"
+
+#include <QList>
+
+#include <functional>
+#include <map>
+
+auto Mempool::calcCompactFeeHistogram(double binSize) const -> FeeHistogramVec
+{
+    FeeHistogramVec ret;
+    std::map<unsigned, unsigned, std::greater<unsigned>> histogram; // sorted map, descending order by key
+
+    for (const auto & [txid, tx] : txs) {
+        const auto feeRate = unsigned(tx->fee / bitcoin::Amount::satoshi()) // sats
+                             /  std::max(tx->sizeBytes, 1u); // per byte
+        histogram[feeRate] += tx->sizeBytes; // accumulate size by feeRate
+    }
+
+    // now, compact the bins
+    ret.reserve(8);
+    unsigned cumSize = 0;
+    double r = 0.;
+
+    for (const auto & [feeRate, size] : histogram) {
+        cumSize += size;
+        if (cumSize + r > binSize) {
+            ret.emplace_back(FeeHistogramItem{feeRate, cumSize});
+            r += double(cumSize) - binSize;
+            cumSize = 0;
+            binSize *= 1.1;
+        }
+    }
+    ret.shrink_to_fit(); // save memory
+    return ret;
+}
diff --git a/Mempool.h b/Mempool.h
index 6c0439a..0e6fac3 100644
--- a/Mempool.h
+++ b/Mempool.h
@@ -131,4 +131,16 @@ struct Mempool
         hashXTxs.reserve(size_t(hxSize*0.75));
         nextOrdinal = 0;
     }
+
+    // -- Fee histogram support (used by mempool.get_fee_histogram RPC) --
+
+    struct FeeHistogramItem {
+        unsigned feeRate = 0; // in sats/B, quotient truncated to uint.
+        unsigned cumulativeSize = 0; // bin size, cumulative bytes
+    };
+    using FeeHistogramVec = std::vector<FeeHistogramItem>;
+    /// This function is potentially going to take a few ms (or more) on large mempools, so call this from a background
+    /// task that updates a cached histogram. If calling this from threaded code with a shared mempool, be sure to call
+    /// it with the appropriate locks held.
+    FeeHistogramVec calcCompactFeeHistogram(double binSize = 1e5 /* binSize in bytes */) const;
 };