diff --git a/x-pack/plugins/apm/server/lib/transaction_groups/__snapshots__/fetcher.test.ts.snap b/x-pack/plugins/apm/server/lib/transaction_groups/__snapshots__/fetcher.test.ts.snap
index 07f8bf59f53a0..3701094ba818b 100644
--- a/x-pack/plugins/apm/server/lib/transaction_groups/__snapshots__/fetcher.test.ts.snap
+++ b/x-pack/plugins/apm/server/lib/transaction_groups/__snapshots__/fetcher.test.ts.snap
@@ -37,11 +37,16 @@ Array [
                   ],
                 },
               },
+              "sum": Object {
+                "sum": Object {
+                  "field": "transaction.duration.us",
+                },
+              },
             },
             "terms": Object {
               "field": "transaction.name.keyword",
               "order": Object {
-                "avg": "desc",
+                "sum": "desc",
               },
               "size": 100,
             },
diff --git a/x-pack/plugins/apm/server/lib/transaction_groups/__snapshots__/transform.test.ts.snap b/x-pack/plugins/apm/server/lib/transaction_groups/__snapshots__/transform.test.ts.snap
index a68d7dc80338a..2d8b16e95f769 100644
--- a/x-pack/plugins/apm/server/lib/transaction_groups/__snapshots__/transform.test.ts.snap
+++ b/x-pack/plugins/apm/server/lib/transaction_groups/__snapshots__/transform.test.ts.snap
@@ -4,7 +4,7 @@ exports[`transactionGroupsTransformer should match snapshot 1`] = `
 Array [
   Object {
     "averageResponseTime": 255966.30555555556,
-    "impact": 4.369340653255684,
+    "impact": 4.3693406535517445,
     "name": "POST /api/orders",
     "p95": 320238.5,
     "sample": Object {
@@ -255,7 +255,7 @@ baz",
   },
   Object {
     "averageResponseTime": 33265.03326147213,
-    "impact": 10.256357027900046,
+    "impact": 10.256357027376065,
     "name": "GET /api/orders",
     "p95": 58827.489999999976,
     "sample": Object {
@@ -376,7 +376,7 @@ baz",
   },
   Object {
     "averageResponseTime": 32900.72714285714,
-    "impact": 2.179120743402716,
+    "impact": 2.1791207411745854,
     "name": "GET /log-message",
     "p95": 40444,
     "sample": Object {
@@ -497,7 +497,7 @@ baz",
   },
   Object {
     "averageResponseTime": 32554.36257814184,
-    "impact": 14.344171564855404,
+    "impact": 14.344171563678346,
     "name": "GET /api/stats",
     "p95": 59356.73611111111,
     "sample": Object {
@@ -624,7 +624,7 @@ baz",
   },
   Object {
     "averageResponseTime": 32387.73641304348,
-    "impact": 2.2558112391673664,
+    "impact": 2.2558112380477584,
     "name": "GET /log-error",
     "p95": 40061.1,
     "sample": Object {
@@ -745,7 +745,7 @@ baz",
   },
   Object {
     "averageResponseTime": 32159.926322043968,
-    "impact": 10.279049521913821,
+    "impact": 10.27904952170656,
     "name": "GET /api/customers",
     "p95": 59845.85714285714,
     "sample": Object {
@@ -872,7 +872,7 @@ baz",
   },
   Object {
     "averageResponseTime": 27516.89144558744,
-    "impact": 9.651458993728006,
+    "impact": 9.651458992731666,
     "name": "GET /api/products/top",
     "p95": 56064.679999999986,
     "sample": Object {
@@ -1000,7 +1000,7 @@ baz",
   },
   Object {
     "averageResponseTime": 21331.714285714286,
-    "impact": 0.28817488008070574,
+    "impact": 0.28817487960409877,
     "name": "POST /api",
     "p95": 30938,
     "sample": Object {
@@ -1123,7 +1123,7 @@ baz",
   },
   Object {
     "averageResponseTime": 17189.329210275926,
-    "impact": 3.424381788267164,
+    "impact": 3.424381787142002,
     "name": "GET /api/products/:id/customers",
     "p95": 39284.79999999999,
     "sample": Object {
@@ -1250,7 +1250,7 @@ baz",
   },
   Object {
     "averageResponseTime": 12763.68806073154,
-    "impact": 1.747992435179465,
+    "impact": 1.7479924334286208,
     "name": "GET /api/types/:id",
     "p95": 30576.749999999996,
     "sample": Object {
@@ -1371,7 +1371,7 @@ baz",
   },
   Object {
     "averageResponseTime": 12683.190864600327,
-    "impact": 4.4239778511514745,
+    "impact": 4.4239778504968,
     "name": "GET /api/products",
     "p95": 35009.67999999999,
     "sample": Object {
@@ -1492,7 +1492,7 @@ baz",
   },
   Object {
     "averageResponseTime": 11257.757916666667,
-    "impact": 2.558180605423081,
+    "impact": 2.558180605569336,
     "name": "GET /api/types",
     "p95": 35222.944444444445,
     "sample": Object {
@@ -1613,7 +1613,7 @@ baz",
   },
   Object {
     "averageResponseTime": 10584.05144193297,
-    "impact": 1.2808106158729446,
+    "impact": 1.280810614916383,
     "name": "GET /api/orders/:id",
     "p95": 26555.399999999998,
     "sample": Object {
@@ -1732,7 +1732,7 @@ baz",
   },
   Object {
     "averageResponseTime": 10548.218597063622,
-    "impact": 1.8338764008269306,
+    "impact": 1.8338763992340905,
     "name": "GET /api/products/:id",
     "p95": 28413.383333333328,
     "sample": Object {
@@ -1853,7 +1853,7 @@ baz",
   },
   Object {
     "averageResponseTime": 9868.217894736843,
-    "impact": 1.7722323979309487,
+    "impact": 1.7722323960215767,
     "name": "GET /api/customers/:id",
     "p95": 27486.5,
     "sample": Object {
@@ -2111,7 +2111,7 @@ baz",
   },
   Object {
     "averageResponseTime": 4694.005586592179,
-    "impact": 0.1498514997591876,
+    "impact": 0.1498515000753004,
     "name": "GET /is-it-coffee-time",
     "p95": 11022.99999999992,
     "sample": Object {
@@ -2233,7 +2233,7 @@ baz",
   },
   Object {
     "averageResponseTime": 4549.889880952381,
-    "impact": 0.1354336505457395,
+    "impact": 0.13543365054509587,
     "name": "GET /throw-error",
     "p95": 7719.700000000001,
     "sample": Object {
@@ -2355,7 +2355,7 @@ baz",
   },
   Object {
     "averageResponseTime": 3504.5108924806746,
-    "impact": 2.36009934580083,
+    "impact": 2.3600993453143766,
     "name": "GET *",
     "p95": 11431.738095238095,
     "sample": Object {
@@ -2482,7 +2482,7 @@ baz",
   },
   Object {
     "averageResponseTime": 2742.4615384615386,
-    "impact": 0.08501029113483448,
+    "impact": 0.08501028923348058,
     "name": "OPTIONS unknown route",
     "p95": 4370.000000000002,
     "sample": Object {
@@ -2605,7 +2605,7 @@ baz",
   },
   Object {
     "averageResponseTime": 2651.8784461553205,
-    "impact": 15.770246498769827,
+    "impact": 15.770246496477105,
     "name": "GET static file",
     "p95": 6140.579335038363,
     "sample": Object {
@@ -2713,7 +2713,7 @@ baz",
   },
   Object {
     "averageResponseTime": 1422.926672899693,
-    "impact": 1.002712481568783,
+    "impact": 1.0027124806135428,
     "name": "GET unknown route",
     "p95": 2311.885238095238,
     "sample": Object {
diff --git a/x-pack/plugins/apm/server/lib/transaction_groups/fetcher.ts b/x-pack/plugins/apm/server/lib/transaction_groups/fetcher.ts
index 2a534aa3315f1..ad0aa00d35bc9 100644
--- a/x-pack/plugins/apm/server/lib/transaction_groups/fetcher.ts
+++ b/x-pack/plugins/apm/server/lib/transaction_groups/fetcher.ts
@@ -16,14 +16,9 @@ import { Setup } from '../helpers/setup_request';
 interface Bucket {
   key: string;
   doc_count: number;
-  avg: {
-    value: number;
-  };
-  p95: {
-    values: {
-      '95.0': number;
-    };
-  };
+  avg: { value: number };
+  p95: { values: { '95.0': number } };
+  sum: { value: number };
   sample: {
     hits: {
       total: number;
@@ -57,7 +52,7 @@ export function transactionGroupsFetcher(
         transactions: {
           terms: {
             field: `${TRANSACTION_NAME}.keyword`,
-            order: { avg: 'desc' },
+            order: { sum: 'desc' },
             size: 100
           },
           aggs: {
@@ -73,7 +68,8 @@ export function transactionGroupsFetcher(
             avg: { avg: { field: TRANSACTION_DURATION } },
             p95: {
               percentiles: { field: TRANSACTION_DURATION, percents: [95] }
-            }
+            },
+            sum: { sum: { field: TRANSACTION_DURATION } }
           }
         }
       }
diff --git a/x-pack/plugins/apm/server/lib/transaction_groups/mock-responses/transactionGroupsResponse.ts b/x-pack/plugins/apm/server/lib/transaction_groups/mock-responses/transactionGroupsResponse.ts
index 08492ee7a7839..2632cc6e94b93 100644
--- a/x-pack/plugins/apm/server/lib/transaction_groups/mock-responses/transactionGroupsResponse.ts
+++ b/x-pack/plugins/apm/server/lib/transaction_groups/mock-responses/transactionGroupsResponse.ts
@@ -21,6 +21,7 @@ export const transactionGroupsResponse = ({
           doc_count: 180,
           avg: { value: 255966.30555555556 },
           p95: { values: { '95.0': 320238.5 } },
+          sum: { value: 46073935 },
           sample: {
             hits: {
               total: 180,
@@ -140,6 +141,7 @@ export const transactionGroupsResponse = ({
           doc_count: 21911,
           avg: { value: 48021.972616494 },
           p95: { values: { '95.0': 67138.18364917398 } },
+          sum: { value: 1052209442 },
           sample: {
             hits: {
               total: 21911,
@@ -259,6 +261,7 @@ export const transactionGroupsResponse = ({
           doc_count: 3247,
           avg: { value: 33265.03326147213 },
           p95: { values: { '95.0': 58827.489999999976 } },
+          sum: { value: 108011563 },
           sample: {
             hits: {
               total: 3247,
@@ -374,6 +377,7 @@ export const transactionGroupsResponse = ({
           doc_count: 700,
           avg: { value: 32900.72714285714 },
           p95: { values: { '95.0': 40444 } },
+          sum: { value: 23030509 },
           sample: {
             hits: {
               total: 700,
@@ -489,6 +493,7 @@ export const transactionGroupsResponse = ({
           doc_count: 4639,
           avg: { value: 32554.36257814184 },
           p95: { values: { '95.0': 59356.73611111111 } },
+          sum: { value: 151019688 },
           sample: {
             hits: {
               total: 4639,
@@ -609,6 +614,7 @@ export const transactionGroupsResponse = ({
           doc_count: 736,
           avg: { value: 32387.73641304348 },
           p95: { values: { '95.0': 40061.1 } },
+          sum: { value: 23837374 },
           sample: {
             hits: {
               total: 736,
@@ -724,6 +730,7 @@ export const transactionGroupsResponse = ({
           doc_count: 3366,
           avg: { value: 32159.926322043968 },
           p95: { values: { '95.0': 59845.85714285714 } },
+          sum: { value: 108250312 },
           sample: {
             hits: {
               total: 3366,
@@ -844,6 +851,7 @@ export const transactionGroupsResponse = ({
           doc_count: 3694,
           avg: { value: 27516.89144558744 },
           p95: { values: { '95.0': 56064.679999999986 } },
+          sum: { value: 101647397 },
           sample: {
             hits: {
               total: 3694,
@@ -965,6 +973,7 @@ export const transactionGroupsResponse = ({
           doc_count: 147,
           avg: { value: 21331.714285714286 },
           p95: { values: { '95.0': 30938 } },
+          sum: { value: 3135762 },
           sample: {
             hits: {
               total: 147,
@@ -1082,6 +1091,7 @@ export const transactionGroupsResponse = ({
           doc_count: 2102,
           avg: { value: 17189.329210275926 },
           p95: { values: { '95.0': 39284.79999999999 } },
+          sum: { value: 36131970 },
           sample: {
             hits: {
               total: 2102,
@@ -1203,6 +1213,7 @@ export const transactionGroupsResponse = ({
           doc_count: 1449,
           avg: { value: 12763.68806073154 },
           p95: { values: { '95.0': 30576.749999999996 } },
+          sum: { value: 18494584 },
           sample: {
             hits: {
               total: 1449,
@@ -1318,6 +1329,7 @@ export const transactionGroupsResponse = ({
           doc_count: 3678,
           avg: { value: 12683.190864600327 },
           p95: { values: { '95.0': 35009.67999999999 } },
+          sum: { value: 46648776 },
           sample: {
             hits: {
               total: 3678,
@@ -1433,6 +1445,7 @@ export const transactionGroupsResponse = ({
           doc_count: 2400,
           avg: { value: 11257.757916666667 },
           p95: { values: { '95.0': 35222.944444444445 } },
+          sum: { value: 27018619 },
           sample: {
             hits: {
               total: 2400,
@@ -1548,6 +1561,7 @@ export const transactionGroupsResponse = ({
           doc_count: 1283,
           avg: { value: 10584.05144193297 },
           p95: { values: { '95.0': 26555.399999999998 } },
+          sum: { value: 13579338 },
           sample: {
             hits: {
               total: 1283,
@@ -1661,6 +1675,7 @@ export const transactionGroupsResponse = ({
           doc_count: 1839,
           avg: { value: 10548.218597063622 },
           p95: { values: { '95.0': 28413.383333333328 } },
+          sum: { value: 19398174 },
           sample: {
             hits: {
               total: 1839,
@@ -1776,6 +1791,7 @@ export const transactionGroupsResponse = ({
           doc_count: 1900,
           avg: { value: 9868.217894736843 },
           p95: { values: { '95.0': 27486.5 } },
+          sum: { value: 18749614 },
           sample: {
             hits: {
               total: 1900,
@@ -1896,6 +1912,7 @@ export const transactionGroupsResponse = ({
           doc_count: 20,
           avg: { value: 5192.9 },
           p95: { values: { '95.0': 13230.5 } },
+          sum: { value: 103858 },
           sample: {
             hits: {
               total: 20,
@@ -2021,6 +2038,7 @@ export const transactionGroupsResponse = ({
           doc_count: 358,
           avg: { value: 4694.005586592179 },
           p95: { values: { '95.0': 11022.99999999992 } },
+          sum: { value: 1680454 },
           sample: {
             hits: {
               total: 358,
@@ -2137,6 +2155,7 @@ export const transactionGroupsResponse = ({
           doc_count: 336,
           avg: { value: 4549.889880952381 },
           p95: { values: { '95.0': 7719.700000000001 } },
+          sum: { value: 1528763 },
           sample: {
             hits: {
               total: 336,
@@ -2253,6 +2272,7 @@ export const transactionGroupsResponse = ({
           doc_count: 7115,
           avg: { value: 3504.5108924806746 },
           p95: { values: { '95.0': 11431.738095238095 } },
+          sum: { value: 24934595 },
           sample: {
             hits: {
               total: 7115,
@@ -2375,6 +2395,7 @@ export const transactionGroupsResponse = ({
           doc_count: 364,
           avg: { value: 2742.4615384615386 },
           p95: { values: { '95.0': 4370.000000000002 } },
+          sum: { value: 998256 },
           sample: {
             hits: {
               total: 364,
@@ -2492,6 +2513,7 @@ export const transactionGroupsResponse = ({
           doc_count: 62606,
           avg: { value: 2651.8784461553205 },
           p95: { values: { '95.0': 6140.579335038363 } },
+          sum: { value: 166023502 },
           sample: {
             hits: {
               total: 62606,
@@ -2596,6 +2618,7 @@ export const transactionGroupsResponse = ({
           doc_count: 7487,
           avg: { value: 1422.926672899693 },
           p95: { values: { '95.0': 2311.885238095238 } },
+          sum: { value: 10653452 },
           sample: {
             hits: {
               total: 7487,
diff --git a/x-pack/plugins/apm/server/lib/transaction_groups/transform.test.ts b/x-pack/plugins/apm/server/lib/transaction_groups/transform.test.ts
index 73053aa04643d..6acd34af24353 100644
--- a/x-pack/plugins/apm/server/lib/transaction_groups/transform.test.ts
+++ b/x-pack/plugins/apm/server/lib/transaction_groups/transform.test.ts
@@ -19,12 +19,13 @@ describe('transactionGroupsTransformer', () => {
     ).toMatchSnapshot();
   });
 
-  fit('should transform response correctly', () => {
+  it('should transform response correctly', () => {
     const bucket = {
       key: 'POST /api/orders',
       doc_count: 180,
       avg: { value: 255966.30555555556 },
       p95: { values: { '95.0': 320238.5 } },
+      sum: { value: 3000000000 },
       sample: {
         hits: {
           total: 180,
@@ -54,4 +55,27 @@ describe('transactionGroupsTransformer', () => {
       }
     ]);
   });
+
+  it('should calculate impact from sum', () => {
+    const getBucket = (sum: number) => ({
+      key: 'POST /api/orders',
+      doc_count: 180,
+      avg: { value: 300000 },
+      p95: { values: { '95.0': 320000 } },
+      sum: { value: sum },
+      sample: { hits: { total: 180, hits: [{ _source: 'sample source' }] } }
+    });
+
+    const response = ({
+      aggregations: {
+        transactions: { buckets: [getBucket(10), getBucket(20), getBucket(50)] }
+      }
+    } as unknown) as ESResponse;
+
+    expect(
+      transactionGroupsTransformer({ response, start: 100, end: 20000 }).map(
+        bucket => bucket.impact
+      )
+    ).toEqual([0, 25, 100]);
+  });
 });
diff --git a/x-pack/plugins/apm/server/lib/transaction_groups/transform.ts b/x-pack/plugins/apm/server/lib/transaction_groups/transform.ts
index 229134025b18f..53f8ca04d4ee6 100644
--- a/x-pack/plugins/apm/server/lib/transaction_groups/transform.ts
+++ b/x-pack/plugins/apm/server/lib/transaction_groups/transform.ts
@@ -44,7 +44,7 @@ export function transactionGroupsTransformer({
   const results = buckets.map(bucket => {
     const averageResponseTime = bucket.avg.value;
     const transactionsPerMinute = bucket.doc_count / minutes;
-    const impact = Math.round(averageResponseTime * transactionsPerMinute);
+    const impact = bucket.sum.value;
     const sample = bucket.sample.hits.hits[0]._source;
 
     return {