diff --git a/cmd/zdb/zdb.c b/cmd/zdb/zdb.c
index 763a086ac468..a329e4a8337e 100644
--- a/cmd/zdb/zdb.c
+++ b/cmd/zdb/zdb.c
@@ -4161,6 +4161,7 @@ static const char *zdb_ot_extname[] = {
 };
 
 #define	ZB_TOTAL	DN_MAX_LEVELS
+#define	SPA_MAX_FOR_16M	(SPA_MAXBLOCKSHIFT+1)
 
 typedef struct zdb_cb {
 	zdb_blkstats_t	zcb_type[ZB_TOTAL + 1][ZDB_OT_TOTAL + 1];
@@ -4168,6 +4169,15 @@ typedef struct zdb_cb {
 	uint64_t	zcb_checkpoint_size;
 	uint64_t	zcb_dedup_asize;
 	uint64_t	zcb_dedup_blocks;
+	uint64_t	zcb_psize_count[SPA_MAX_FOR_16M];
+	uint64_t	zcb_lsize_count[SPA_MAX_FOR_16M];
+	uint64_t	zcb_asize_count[SPA_MAX_FOR_16M];
+	uint64_t	zcb_psize_len[SPA_MAX_FOR_16M];
+	uint64_t	zcb_lsize_len[SPA_MAX_FOR_16M];
+	uint64_t	zcb_asize_len[SPA_MAX_FOR_16M];
+	uint64_t	zcb_psize_total;
+	uint64_t	zcb_lsize_total;
+	uint64_t	zcb_asize_total;
 	uint64_t	zcb_embedded_blocks[NUM_BP_EMBEDDED_TYPES];
 	uint64_t	zcb_embedded_histogram[NUM_BP_EMBEDDED_TYPES]
 	    [BPE_PAYLOAD_SIZE + 1];
@@ -4191,6 +4201,172 @@ same_metaslab(spa_t *spa, uint64_t vdev, uint64_t off1, uint64_t off2)
 	return ((off1 >> ms_shift) == (off2 >> ms_shift));
 }
 
+/*
+ * Used to simplify reporting of the histogram data.
+ */
+typedef struct one_histo {
+	char *name;
+	uint64_t *count;
+	uint64_t *len;
+	uint64_t cumulative;
+} one_histo_t;
+
+/*
+ * The number of separate histograms processed for psize, lsize and asize.
+ */
+#define	NUM_HISTO 3
+
+/*
+ * This routine will create a fixed column size output of three different
+ * histograms showing by blocksize of 512 - 2^ SPA_MAX_FOR_16M
+ * the count, length and cumulative length of the psize, lsize and
+ * asize blocks.
+ *
+ * All three types of blocks are listed on a single line
+ *
+ * By default the table is printed in nicenumber format (e.g. 123K) but
+ * if the '-P' parameter is specified then the full raw number (parseable)
+ * is printed out.
+ */
+static void
+dump_size_histograms(zdb_cb_t *zcb)
+{
+	/*
+	 * A temporary buffer that allows us to convert a number into
+	 * a string using zdb_nicenumber to allow either raw or human
+	 * readable numbers to be output.
+	 */
+	char numbuf[32];
+
+	/*
+	 * Define titles which are used in the headers of the tables
+	 * printed by this routine.
+	 */
+	const char blocksize_title1[] = "block";
+	const char blocksize_title2[] = "size";
+	const char count_title[] = "Count";
+	const char length_title[] = "Size";
+	const char cumulative_title[] = "Cum.";
+
+	/*
+	 * Setup the histogram arrays (psize, lsize, and asize).
+	 */
+	one_histo_t parm_histo[NUM_HISTO];
+
+	parm_histo[0].name = "psize";
+	parm_histo[0].count = zcb->zcb_psize_count;
+	parm_histo[0].len = zcb->zcb_psize_len;
+	parm_histo[0].cumulative = 0;
+
+	parm_histo[1].name = "lsize";
+	parm_histo[1].count = zcb->zcb_lsize_count;
+	parm_histo[1].len = zcb->zcb_lsize_len;
+	parm_histo[1].cumulative = 0;
+
+	parm_histo[2].name = "asize";
+	parm_histo[2].count = zcb->zcb_asize_count;
+	parm_histo[2].len = zcb->zcb_asize_len;
+	parm_histo[2].cumulative = 0;
+
+
+	(void) printf("\nBlock Size Histogram\n");
+	/*
+	 * Print the first line titles
+	 */
+	if (dump_opt['P'])
+		(void) printf("\n%s\t", blocksize_title1);
+	else
+		(void) printf("\n%7s   ", blocksize_title1);
+
+	for (int j = 0; j < NUM_HISTO; j++) {
+		if (dump_opt['P']) {
+			if (j < NUM_HISTO - 1) {
+				(void) printf("%s\t\t\t", parm_histo[j].name);
+			} else {
+				/* Don't print trailing spaces */
+				(void) printf("  %s", parm_histo[j].name);
+			}
+		} else {
+			if (j < NUM_HISTO - 1) {
+				/* Left aligned strings in the output */
+				(void) printf("%-7s              ",
+				    parm_histo[j].name);
+			} else {
+				/* Don't print trailing spaces */
+				(void) printf("%s", parm_histo[j].name);
+			}
+		}
+	}
+	(void) printf("\n");
+
+	/*
+	 * Print the second line titles
+	 */
+	if (dump_opt['P']) {
+		(void) printf("%s\t", blocksize_title2);
+	} else {
+		(void) printf("%7s ", blocksize_title2);
+	}
+
+	for (int i = 0; i < NUM_HISTO; i++) {
+		if (dump_opt['P']) {
+			(void) printf("%s\t%s\t%s\t",
+			    count_title, length_title, cumulative_title);
+		} else {
+			(void) printf("%7s%7s%7s",
+			    count_title, length_title, cumulative_title);
+		}
+	}
+	(void) printf("\n");
+
+	/*
+	 * Print the rows
+	 */
+	for (int i = SPA_MINBLOCKSHIFT; i < SPA_MAX_FOR_16M; i++) {
+
+		/*
+		 * Print the first column showing the blocksize
+		 */
+		zdb_nicenum((1ULL << i), numbuf, sizeof (numbuf));
+
+		if (dump_opt['P']) {
+			printf("%s", numbuf);
+		} else {
+			printf("%7s:", numbuf);
+		}
+
+		/*
+		 * Print the remaining set of 3 columns per size:
+		 * for psize, lsize and asize
+		 */
+		for (int j = 0; j < NUM_HISTO; j++) {
+			parm_histo[j].cumulative += parm_histo[j].len[i];
+
+			zdb_nicenum(parm_histo[j].count[i],
+			    numbuf, sizeof (numbuf));
+			if (dump_opt['P'])
+				(void) printf("\t%s", numbuf);
+			else
+				(void) printf("%7s", numbuf);
+
+			zdb_nicenum(parm_histo[j].len[i],
+			    numbuf, sizeof (numbuf));
+			if (dump_opt['P'])
+				(void) printf("\t%s", numbuf);
+			else
+				(void) printf("%7s", numbuf);
+
+			zdb_nicenum(parm_histo[j].cumulative,
+			    numbuf, sizeof (numbuf));
+			if (dump_opt['P'])
+				(void) printf("\t%s", numbuf);
+			else
+				(void) printf("%7s", numbuf);
+		}
+		(void) printf("\n");
+	}
+}
+
 static void
 zdb_count_block(zdb_cb_t *zcb, zilog_t *zilog, const blkptr_t *bp,
     dmu_object_type_t type)
@@ -4284,6 +4460,28 @@ zdb_count_block(zdb_cb_t *zcb, zilog_t *zilog, const blkptr_t *bp,
 		    [BPE_GET_PSIZE(bp)]++;
 		return;
 	}
+	/*
+	 * The binning histogram bins by powers of two up to
+	 * SPA_MAXBLOCKSIZE rather than creating bins for
+	 * every possible blocksize found in the pool.
+	 */
+	int bin = highbit64(BP_GET_PSIZE(bp)) - 1;
+
+	zcb->zcb_psize_count[bin]++;
+	zcb->zcb_psize_len[bin] += BP_GET_PSIZE(bp);
+	zcb->zcb_psize_total += BP_GET_PSIZE(bp);
+
+	bin = highbit64(BP_GET_LSIZE(bp)) - 1;
+
+	zcb->zcb_lsize_count[bin]++;
+	zcb->zcb_lsize_len[bin] += BP_GET_LSIZE(bp);
+	zcb->zcb_lsize_total += BP_GET_LSIZE(bp);
+
+	bin = highbit64(BP_GET_ASIZE(bp)) - 1;
+
+	zcb->zcb_asize_count[bin]++;
+	zcb->zcb_asize_len[bin] += BP_GET_ASIZE(bp);
+	zcb->zcb_asize_total += BP_GET_ASIZE(bp);
 
 	if (dump_opt['L'])
 		return;
@@ -5645,6 +5843,11 @@ dump_block_stats(spa_t *spa)
 				}
 			}
 		}
+
+		/* Output a table summarizing block sizes in the pool */
+		if (dump_opt['b'] >= 2) {
+			dump_size_histograms(&zcb);
+		}
 	}
 
 	(void) printf("\n");
diff --git a/tests/runfiles/common.run b/tests/runfiles/common.run
index d8c109eb7ddc..765ffea8a302 100644
--- a/tests/runfiles/common.run
+++ b/tests/runfiles/common.run
@@ -104,8 +104,9 @@ tags = ['functional', 'clean_mirror']
 
 [tests/functional/cli_root/zdb]
 tests = ['zdb_002_pos', 'zdb_003_pos', 'zdb_004_pos', 'zdb_005_pos',
-    'zdb_006_pos', 'zdb_args_neg', 'zdb_args_pos', 'zdb_checksum', 'zdb_decompress',
-    'zdb_object_range_neg', 'zdb_object_range_pos', 'zdb_display_block',
+    'zdb_006_pos', 'zdb_args_neg', 'zdb_args_pos',
+    'zdb_block_size_histogram', 'zdb_checksum', 'zdb_decompress',
+    'zdb_display_block', 'zdb_object_range_neg', 'zdb_object_range_pos',
     'zdb_objset_id']
 pre =
 post =
diff --git a/tests/zfs-tests/tests/functional/cli_root/zdb/Makefile.am b/tests/zfs-tests/tests/functional/cli_root/zdb/Makefile.am
index e332a91a856a..3cf13f3ae60e 100644
--- a/tests/zfs-tests/tests/functional/cli_root/zdb/Makefile.am
+++ b/tests/zfs-tests/tests/functional/cli_root/zdb/Makefile.am
@@ -7,6 +7,7 @@ dist_pkgdata_SCRIPTS = \
 	zdb_006_pos.ksh \
 	zdb_args_neg.ksh \
 	zdb_args_pos.ksh \
+	zdb_block_size_histogram.ksh \
 	zdb_checksum.ksh \
 	zdb_decompress.ksh \
 	zdb_object_range_neg.ksh \
diff --git a/tests/zfs-tests/tests/functional/cli_root/zdb/zdb_block_size_histogram.ksh b/tests/zfs-tests/tests/functional/cli_root/zdb/zdb_block_size_histogram.ksh
new file mode 100755
index 000000000000..0c949f9839e1
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/cli_root/zdb/zdb_block_size_histogram.ksh
@@ -0,0 +1,272 @@
+#!/bin/ksh -p
+
+#
+# This file and its contents are supplied under the terms of the
+# Common Development and Distribution License ("CDDL"), version 1.0.
+# You may only use this file in accordance with the terms of version
+# 1.0 of the CDDL.
+#
+# A full copy of the text of the CDDL should have accompanied this
+# source.  A copy of the CDDL is also available via the Internet at
+# http://www.illumos.org/license/CDDL.
+#
+
+#
+# Copyright (c) 2017 by Delphix. All rights reserved.
+# Copyright (c) 2020 by Lawrence Livermore National Security LLC.
+
+. $STF_SUITE/include/libtest.shlib
+
+
+#
+# DESCRIPTION:
+#	Create a pool and populate it with files of various
+#	recordsizes
+#
+# STRATEGY:
+#	1. Create pool
+#	2. Populate it
+#	3. Run zdb -Pbbb on pool
+#	4. Verify variance on blocksizes
+#
+function cleanup
+{
+	datasetexists $TESTPOOL && destroy_pool $TESTPOOL
+}
+
+SPA_MAXBLOCKSHIFT=24
+
+function histo_populate_test_pool
+{
+	if [ $# -ne 1 ]; then
+		log_note "histo_populate_test_pool: insufficient parameters"
+		log_fail "hptp: 1 requested $# received"
+	fi
+	typeset pool=$1
+
+	set -A recordsizes
+	typeset -i min_rsbits=9 #512
+	typeset -i max_rsbits=SPA_MAXBLOCKSHIFT #16 MiB
+	typeset -i sum_filesizes=0
+	re_number='^[0-9]+$'
+
+	let histo_pool_size=$(get_pool_prop size ${pool})
+	if [[ ! ${histo_pool_size} =~ ${re_number} ]]; then
+		log_fail "histo_pool_size is not numeric ${pool_size}"
+	fi
+	let max_pool_record_size=$(get_prop recordsize ${pool})
+	if [[ ! ${max_pool_record_size} =~ ${re_number} ]]; then
+		log_fail "hptp: max_pool_record_size is not numeric ${max_pool_record_size}"
+	fi
+
+	sum_filesizes=$(echo "2^21"|bc)
+	((min_pool_size=12*sum_filesizes))
+	if [ ${histo_pool_size} -lt ${min_pool_size} ]; then
+		log_note "hptp: Your pool size ${histo_pool_size}"
+		log_fail "hptp: is less than minimum ${min_pool_size}"
+	fi
+	this_ri=min_rsbits
+	file_num=0
+	total_count=0
+	###################
+	# generate 10% + 20% + 30% + 31% = 91% of the filespace
+	# attempting to use 100% will lead to no space left on device
+	# Heuristic testing showed that 91% was the practical upper
+	# bound on the default 4G zpool (mirrored) that is used in
+	# testing.
+	#
+	# In order to expedite testing, we will only fill 2G (of 4G)
+	# of the test pool.  You may want to modify this for
+	# standalone testing.
+	# 
+	# In filling only 50% of the pool, we create one object on
+	# each "pass" below to achieve multiple objects per record
+	# size.  Creating one file per object would lead to 
+	# excessive file creation time.
+	###################
+	# for pass in 10 20 30 31  # 91%
+	for pass in 20 20 10 # 50%
+	do
+		((thiscount=(((histo_pool_size*pass)/100)/sum_filesizes)))
+
+		((total_count+=thiscount))
+		for rb in $(seq ${min_rsbits} ${max_rsbits})
+		do
+			this_rs=$(echo "2^${rb}" | bc)
+			if [ ${this_rs} -gt ${max_pool_record_size} ]; then
+				continue
+			fi
+	
+			if [ ! -d /${pool}/B_${this_rs} ]; then
+				zfs create ${pool}/B_${this_rs}
+				zfs set recordsize=${this_rs} \
+				    ${pool}/B_${this_rs}
+			fi
+			####################
+			# Create the files in the devices and datasets
+			# of the right size.  The files are filled
+			# with random data to defeat the compression
+			#
+			# Note that the dd output is suppressed unless
+			# there are errors
+			####################
+
+			dd if=/dev/urandom \
+			    of=/${pool}/B_${this_rs}/file_${filenum} \
+			    bs=${this_rs} count=${thiscount} \
+			    iflag=fullblock 2>&1 | \
+			    egrep -v -e "records in" -e "records out" \
+				-e "bytes.*copied"
+			((filenum+=1))
+		done
+	done
+
+	####################
+	# Testing showed that on some devices, unless the pool is 
+	# synchronized, that the block counts will be below the 
+	# anticipated sizes since not all of the blocks will be flushed
+	# to the device.  This 'sync' command prevents that from 
+	# happening.
+	####################
+	log_must zpool sync ${pool}
+}
+function histo_check_test_pool
+{
+	if [ $# -ne 1 ]; then
+		log_note "histo_check_test_pool: insufficient parameters"
+		log_fail "hctp: 1 requested $# received"
+	fi	
+	typeset pool=$1
+
+	set -A recordsizes
+	set -A recordcounts
+	typeset -i rb
+	typeset -i min_rsbits=9 #512
+	typeset -i max_rsbits=SPA_MAXBLOCKSHIFT+1
+	typeset -i this_rs
+	typeset -i this_ri
+	typeset -i sum_filesizes=0
+	typeset dumped
+	typeset stripped
+
+	let histo_check_pool_size=$(get_pool_prop size ${pool})
+	if [[ ! ${histo_check_pool_size} =~ ${re_number} ]]; then
+		log_fail "histo_check_pool_size is not numeric ${histo_check_pool_size}"
+	fi
+	let max_pool_record_size=$(get_prop recordsize ${pool})
+	if [[ ! ${max_pool_record_size} =~ ${re_number} ]]; then
+		log_fail "hctp: max_pool_record_size is not numeric ${max_pool_record_size}"
+	fi
+
+	dumped="${TEST_BASE_DIR}/${pool}_dump.txt"
+	stripped="${TEST_BASE_DIR}/${pool}_stripped.txt"
+
+	zdb -Pbbb ${pool} | \
+	    tee ${dumped} | \
+	    sed -e '1,/^block[ 	][ 	]*psize[ 	][ 	]*lsize.*$/d' \
+	    -e '/^size[ 	]*Count/d' -e '/^$/,$d' \
+	    > ${stripped}
+
+	sum_filesizes=$(echo "2^21"|bc)
+
+	###################
+	# generate 10% + 20% + 30% + 31% = 91% of the filespace
+	# attempting to use 100% will lead to no space left on device
+	# attempting to use 100% will lead to no space left on device
+	# Heuristic testing showed that 91% was the practical upper
+	# bound on the default 4G zpool (mirrored) that is used in
+	# testing.
+	#
+	# In order to expedite testing, we will only fill 2G (of 4G)
+	# of the test pool.  You may want to modify this for
+	# standalone testing.
+	# 
+	# In filling only 50% of the pool, we create one object on
+	# each "pass" below to achieve multiple objects per record
+	# size.  Creating one file per object would lead to 
+	# excessive file creation time.
+	###################
+	# for pass in 10 20 30 31  # 91%
+	for pass in 20 20 10 # 50%
+	do
+		((thiscount=(((histo_check_pool_size*pass)/100)/sum_filesizes)))
+
+		for rb in $(seq ${min_rsbits} ${max_rsbits})
+		do
+			blksize=$(echo "2^$rb"|bc)
+			if [ $blksize -le $max_pool_record_size ]; then
+				((recordcounts[$blksize]+=thiscount))
+			fi
+		done
+	done
+
+	###################
+	# compare the above computed counts for blocks against
+	# lsize count.  Since some devices have a minimum hardware
+	# blocksize > 512, we cannot compare against the asize count.
+	# E.G., if the HWBlocksize = 4096, then the asize counts for
+	# 512, 1024 and 2048 will be zero and rolled up into the 
+	# 4096 blocksize count for asize.   For verification we stick
+	# to just lsize counts.
+	#
+	# The max_variance is hard-coded here at 10%.  testing so far
+	# has shown this to be in the range of 2%-8% so we leave a
+	# generous allowance... This might need changes in the future
+	###################
+	let max_variance=10
+	let fail_value=0
+	let error_count=0
+	log_note "Comparisons for ${pool}"
+	log_note "Bsize is the blocksize, Count is predicted value"
+	log_note "Bsize\tCount\tpsize\tlsize\tasize"
+	while read -r blksize pc pl pm lc ll lm ac al am
+	do
+		if [ $blksize -gt $max_pool_record_size ]; then
+			continue
+		fi
+		log_note \
+		    "$blksize\t${recordcounts[${blksize}]}\t$pc\t$lc\t$ac"
+
+		###################
+		# get the computer record count and compute the
+		# difference percentage in integer arithmetic
+		###################
+		rc=${recordcounts[${blksize}]}
+		((rclc=(rc-lc)<0?lc-rc:rc-lc)) # absolute value
+		((dp=(rclc*100)/rc))
+
+		###################
+		# Check against the allowed variance
+		###################
+		if [ $dp -gt ${max_variance} ]; then
+			log_note \
+			"Expected variance < ${max_variance}% observed ${dp}%"
+			if [ ${dp} -gt ${fail_value} ]; then
+				fail_value=${dp}
+				((error_count++))
+			fi
+		fi
+	done < ${stripped}
+	if [ ${fail_value} -gt 0 ]; then
+		if [ ${error_count} -eq 1 ]; then
+			log_note "hctp: There was ${error_count} error"
+		else
+			log_note "hctp:There were a total of ${error_count} errors"
+		fi
+		log_fail \
+		"hctp: Max variance of ${max_variance}% exceeded, saw ${fail_value}%"
+	fi
+}
+
+log_assert "Verify zdb -Pbbb (block histogram) works as expected"
+log_onexit cleanup
+verify_runnable "global"
+verify_disk_count "$DISKS" 2
+
+default_mirror_setup_noexit $DISKS
+
+histo_populate_test_pool $TESTPOOL
+
+histo_check_test_pool $TESTPOOL
+
+log_pass "Histogram for zdb"