diff --git a/traffic_ops/traffic_ops_golang/cdn/capacity.go b/traffic_ops/traffic_ops_golang/cdn/capacity.go
new file mode 100644
index 0000000000..a1f754ef0c
--- /dev/null
+++ b/traffic_ops/traffic_ops_golang/cdn/capacity.go
@@ -0,0 +1,337 @@
+package cdn
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import (
+	"database/sql"
+	"encoding/json"
+	"errors"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/apache/trafficcontrol/lib/go-log"
+	"github.com/apache/trafficcontrol/lib/go-tc"
+	"github.com/apache/trafficcontrol/traffic_ops/traffic_ops_golang/api"
+)
+
+func GetCapacity(w http.ResponseWriter, r *http.Request) {
+	inf, userErr, sysErr, errCode := api.NewInfo(r, nil, nil)
+	if userErr != nil || sysErr != nil {
+		api.HandleErr(w, r, inf.Tx.Tx, errCode, userErr, sysErr)
+		return
+	}
+	defer inf.Close()
+
+	api.RespWriter(w, r, inf.Tx.Tx)(getCapacity(inf.Tx.Tx))
+}
+
+const MonitorProxyParameter = "tm.traffic_mon_fwd_proxy"
+const MonitorRequestTimeout = time.Second * 10
+const MonitorOnlineStatus = "ONLINE"
+
+// CRStates contains the Monitor CRStates members needed for health. It is NOT the full object served by the Monitor, but only the data required by this endpoint.
+type CRStates struct {
+	Caches map[tc.CacheName]Available `json:"caches"`
+}
+
+type Available struct {
+	IsAvailable bool `json:"isAvailable"`
+}
+
+// CRConfig contains the Monitor CRConfig members needed for health. It is NOT the full object served by the Monitor, but only the data required by this endpoint.
+type CRConfig struct {
+	ContentServers map[tc.CacheName]CRConfigServer `json:"contentServers"`
+}
+
+type CRConfigServer struct {
+	CacheGroup tc.CacheGroupName `json:"locationId"`
+	Status     tc.CacheStatus    `json:"status"`
+	Type       tc.CacheType      `json:"type"`
+	Profile    string            `json:"profile"`
+}
+
+func getCapacity(tx *sql.Tx) (CapacityResp, error) {
+	monitors, err := getCDNMonitorFQDNs(tx)
+	if err != nil {
+		return CapacityResp{}, errors.New("getting monitors: " + err.Error())
+	}
+
+	return getMonitorsCapacity(tx, monitors)
+}
+
+type CapacityResp struct {
+	AvailablePercent   float64 `json:"availablePercent"`
+	UnavailablePercent float64 `json:"unavailablePercent"`
+	UtilizedPercent    float64 `json:utilizedPercent"`
+	MaintenancePercent float64 `json:maintenancePercent"`
+}
+
+type CapData struct {
+	Available   float64
+	Unavailable float64
+	Utilized    float64
+	Maintenance float64
+	Capacity    float64
+}
+
+func getMonitorsCapacity(tx *sql.Tx, monitors map[tc.CDNName][]string) (CapacityResp, error) {
+	monitorForwardProxy, monitorForwardProxyExists, err := getGlobalParam(tx, MonitorProxyParameter)
+	if err != nil {
+		return CapacityResp{}, errors.New("getting global monitor proxy parameter: " + err.Error())
+	}
+	client := &http.Client{Timeout: MonitorRequestTimeout}
+	if monitorForwardProxyExists {
+		proxyURI, err := url.Parse(monitorForwardProxy)
+		if err != nil {
+			return CapacityResp{}, errors.New("monitor forward proxy '" + monitorForwardProxy + "' in parameter '" + MonitorProxyParameter + "' not a URI: " + err.Error())
+		}
+		client = &http.Client{Timeout: MonitorRequestTimeout, Transport: &http.Transport{Proxy: http.ProxyURL(proxyURI)}}
+	}
+
+	thresholds, err := getEdgeProfileHealthThresholdBandwidth(tx)
+	if err != nil {
+		return CapacityResp{}, errors.New("getting profile thresholds: " + err.Error())
+	}
+
+	cap, err := getCapacityData(monitors, thresholds, client)
+	if err != nil {
+		return CapacityResp{}, errors.New("getting capacity from monitors: " + err.Error())
+	} else if cap.Capacity == 0 {
+		return CapacityResp{}, errors.New("capacity was zero!") // avoid divide-by-zero below.
+	}
+
+	return CapacityResp{
+		UtilizedPercent:    (cap.Available * 100) / cap.Capacity,
+		UnavailablePercent: (cap.Unavailable * 100) / cap.Capacity,
+		MaintenancePercent: (cap.Maintenance * 100) / cap.Capacity,
+		AvailablePercent:   ((cap.Capacity - cap.Unavailable - cap.Maintenance - cap.Available) * 100) / cap.Capacity,
+	}, nil
+}
+
+// getCapacityData attempts to get the CDN capacity from each monitor. If one fails, it tries the next.
+// The first monitor for which all data requests succeed is used.
+// Only if all monitors for a CDN fail is an error returned, from the last monitor tried.
+func getCapacityData(monitors map[tc.CDNName][]string, thresholds map[string]float64, client *http.Client) (CapData, error) {
+	cap := CapData{}
+	for cdn, monitorFQDNs := range monitors {
+		err := error(nil)
+		for _, monitorFQDN := range monitorFQDNs {
+			crStates := CRStates{}
+			crConfig := CRConfig{}
+			cacheStats := CacheStats{}
+			if crStates, err = getCRStates(monitorFQDN, client); err != nil {
+				err = errors.New("getting CRStates for CDN '" + string(cdn) + "' monitor '" + monitorFQDN + "': " + err.Error())
+				log.Warnln("getCapacity failed to get CRStates from cdn '" + string(cdn) + " monitor '" + monitorFQDN + "', trying next monitor: " + err.Error())
+				continue
+			}
+			if crConfig, err = getCRConfig(monitorFQDN, client); err != nil {
+				err = errors.New("getting CRConfig for CDN '" + string(cdn) + "' monitor '" + monitorFQDN + "': " + err.Error())
+				log.Warnln("getCapacity failed to get CRConfig from cdn '" + string(cdn) + " monitor '" + monitorFQDN + "', trying next monitor: " + err.Error())
+				continue
+			}
+			if err := getCacheStats(monitorFQDN, client, []string{"kbps", "maxKbps"}, &cacheStats); err != nil {
+				err = errors.New("getting cache stats for CDN '" + string(cdn) + "' monitor '" + monitorFQDN + "': " + err.Error())
+				log.Warnln("getCapacity failed to get CacheStats from cdn '" + string(cdn) + " monitor '" + monitorFQDN + "', trying next monitor: " + err.Error())
+				continue
+			}
+			cap = addCapacity(cap, cacheStats, crStates, crConfig, thresholds)
+			break
+		}
+		if err != nil {
+			return CapData{}, err
+		}
+	}
+	return cap, nil
+}
+
+func addCapacity(cap CapData, cacheStats CacheStats, crStates CRStates, crConfig CRConfig, thresholds map[string]float64) CapData {
+	for cacheName, stats := range cacheStats.Caches {
+		cache, ok := crConfig.ContentServers[cacheName]
+		if !ok {
+			continue
+		}
+		if !strings.HasPrefix(string(cache.Type), string(tc.CacheTypeEdge)) {
+			continue
+		}
+		if len(stats.KBPS) < 1 || len(stats.MaxKBPS) < 1 {
+			continue
+		}
+		if cache.Status == "REPORTED" || cache.Status == "ONLINE" {
+			if crStates.Caches[cacheName].IsAvailable {
+				cap.Available += float64(stats.KBPS[0].Value)
+			} else {
+				cap.Unavailable += float64(stats.KBPS[0].Value)
+			}
+		} else if cache.Status == "ADMIN_DOWN" {
+			cap.Maintenance += float64(stats.KBPS[0].Value)
+		} else {
+			continue // don't add capacity for OFFLINE or other statuses
+		}
+		cap.Capacity += float64(stats.MaxKBPS[0].Value) - thresholds[cache.Profile]
+	}
+	return cap
+}
+
+func getEdgeProfileHealthThresholdBandwidth(tx *sql.Tx) (map[string]float64, error) {
+	rows, err := tx.Query(`
+SELECT pr.name as profile, pa.name, pa.config_file, pa.value
+FROM parameter as pa
+JOIN profile_parameter as pp ON pp.parameter = pa.id
+JOIN profile as pr ON pp.profile = pr.id
+JOIN server as s ON s.profile = pr.id
+JOIN cdn as c ON c.id = s.cdn_id
+JOIN type as t ON s.type = t.id
+WHERE t.name LIKE 'EDGE%'
+AND pa.config_file = 'rascal-config.txt'
+AND pa.name = 'health.threshold.availableBandwidthInKbps'
+`)
+	if err != nil {
+		return nil, errors.New("querying thresholds: " + err.Error())
+	}
+	defer rows.Close()
+	profileThresholds := map[string]float64{}
+	for rows.Next() {
+		profile := ""
+		threshStr := ""
+		if err := rows.Scan(&profile, &threshStr); err != nil {
+			return nil, errors.New("scanning thresholds: " + err.Error())
+		}
+		threshStr = strings.TrimPrefix(threshStr, ">")
+		thresh, err := strconv.ParseFloat(threshStr, 64)
+		if err != nil {
+			return nil, errors.New("profile '" + profile + "' health.threshold.availableBandwidthInKbps is not a number")
+		}
+		profileThresholds[profile] = thresh
+	}
+	return profileThresholds, nil
+}
+
+func getCRStates(monitorFQDN string, client *http.Client) (CRStates, error) {
+	path := `/publish/CrStates`
+	resp, err := client.Get("http://" + monitorFQDN + path)
+	if err != nil {
+		return CRStates{}, errors.New("getting CRStates from Monitor '" + monitorFQDN + "': " + err.Error())
+	}
+	defer resp.Body.Close()
+
+	crs := CRStates{}
+	if err := json.NewDecoder(resp.Body).Decode(&crs); err != nil {
+		return CRStates{}, errors.New("decoding CRStates from monitor '" + monitorFQDN + "': " + err.Error())
+	}
+	return crs, nil
+}
+
+func getCRConfig(monitorFQDN string, client *http.Client) (CRConfig, error) {
+	path := `/publish/CrConfig`
+	resp, err := client.Get("http://" + monitorFQDN + path)
+	if err != nil {
+		return CRConfig{}, errors.New("getting CRConfig from Monitor '" + monitorFQDN + "': " + err.Error())
+	}
+	defer resp.Body.Close()
+	crs := CRConfig{}
+	if err := json.NewDecoder(resp.Body).Decode(&crs); err != nil {
+		return CRConfig{}, errors.New("decoding CRConfig from monitor '" + monitorFQDN + "': " + err.Error())
+	}
+	return crs, nil
+}
+
+// CacheStats contains the Monitor CacheStats needed by Cachedata. It is NOT the full object served by the Monitor, but only the data required by the caches stats endpoint.
+type CacheStats struct {
+	Caches map[tc.CacheName]CacheStat `json:"caches"`
+}
+
+type CacheStat struct {
+	KBPS    []CacheStatData `json:"kbps"`
+	MaxKBPS []CacheStatData `json:"maxKbps"`
+}
+
+type CacheStatData struct {
+	Value float64 `json:"value,string"`
+}
+
+// getCacheStats gets the cache stats from the given monitor. It takes stats, a slice of stat names; and cacheStats, an object to deserialize stats into. The cacheStats type must be of the form struct {caches map[tc.CacheName]struct{statName []struct{value float64}}} with the desired stats, with appropriate member names or tags.
+func getCacheStats(monitorFQDN string, client *http.Client, stats []string, cacheStats interface{}) error {
+	path := `/publish/CacheStats`
+	if len(stats) > 0 {
+		path += `?stats=` + strings.Join(stats, `,`)
+	}
+	resp, err := client.Get("http://" + monitorFQDN + path)
+	if err != nil {
+		return errors.New("getting CacheStats from Monitor '" + monitorFQDN + "': " + err.Error())
+	}
+	defer resp.Body.Close()
+	if err := json.NewDecoder(resp.Body).Decode(cacheStats); err != nil {
+		return errors.New("decoding CacheStats from monitor '" + monitorFQDN + "': " + err.Error())
+	}
+	return nil
+}
+
+// getCDNMonitors returns an FQDN, including port, of an online monitor for each CDN. If a CDN has no online monitors, that CDN will not have an entry in the map. If a CDN has multiple online monitors, an arbitrary one will be returned.
+func getCDNMonitorFQDNs(tx *sql.Tx) (map[tc.CDNName][]string, error) {
+	rows, err := tx.Query(`
+SELECT s.host_name, s.domain_name, s.tcp_port, c.name as cdn
+FROM server as s
+JOIN type as t ON s.type = t.id
+JOIN status as st ON st.id = s.status
+JOIN cdn as c ON c.id = s.cdn_id
+WHERE t.name = '` + tc.MonitorTypeName + `'
+AND st.name = '` + MonitorOnlineStatus + `'
+`)
+	if err != nil {
+		return nil, errors.New("querying monitors: " + err.Error())
+	}
+	defer rows.Close()
+	monitors := map[tc.CDNName][]string{}
+	for rows.Next() {
+		host := ""
+		domain := ""
+		port := sql.NullInt64{}
+		cdn := tc.CDNName("")
+		if err := rows.Scan(&host, &domain, &port, &cdn); err != nil {
+			return nil, errors.New("scanning monitors: " + err.Error())
+		}
+		fqdn := host + "." + domain
+		if port.Valid {
+			fqdn += ":" + strconv.FormatInt(port.Int64, 10)
+		}
+		monitors[cdn] = append(monitors[cdn], fqdn)
+	}
+	return monitors, nil
+}
+
+// getGlobalParams returns the value of the global param, whether it existed, or any error
+func getGlobalParam(tx *sql.Tx, name string) (string, bool, error) {
+	return getParam(tx, name, "global")
+}
+
+// getGlobalParams returns the value of the param, whether it existed, or any error.
+func getParam(tx *sql.Tx, name string, configFile string) (string, bool, error) {
+	val := ""
+	if err := tx.QueryRow(`select value from parameter where name = $1 and config_file = $2`, name, configFile).Scan(&val); err != nil {
+		if err == sql.ErrNoRows {
+			return "", false, nil
+		}
+		return "", false, errors.New("Error querying global paramter '" + name + "': " + err.Error())
+	}
+	return val, true, nil
+}
diff --git a/traffic_ops/traffic_ops_golang/routing/routes.go b/traffic_ops/traffic_ops_golang/routing/routes.go
index 50c19c88a3..7b993900a3 100644
--- a/traffic_ops/traffic_ops_golang/routing/routes.go
+++ b/traffic_ops/traffic_ops_golang/routing/routes.go
@@ -122,8 +122,10 @@ func Routes(d ServerData) ([]Route, []RawRoute, http.Handler, error) {
 		//CDN
 		{1.1, http.MethodGet, `cdns/name/{name}/sslkeys/?(\.json)?$`, cdn.GetSSLKeys, auth.PrivLevelAdmin, Authenticated, nil},
 		{1.1, http.MethodGet, `cdns/metric_types`, notImplementedHandler, 0, NoAuth, nil}, // MUST NOT end in $, because the 1.x route is longer
-		{1.1, http.MethodGet, `cdns/capacity$`, handlerToFunc(proxyHandler), 0, NoAuth, []Middleware{}},
+
+		{1.1, http.MethodGet, `cdns/capacity$`, cdn.GetCapacity, auth.PrivLevelReadOnly, Authenticated, nil},
 		{1.1, http.MethodGet, `cdns/configs/?(\.json)?$`, cdn.GetConfigs, auth.PrivLevelReadOnly, Authenticated, nil},
+
 		{1.1, http.MethodGet, `cdns/domains/?(\.json)?$`, cdn.DomainsHandler, auth.PrivLevelReadOnly, Authenticated, nil},
 		{1.1, http.MethodGet, `cdns/health$`, handlerToFunc(proxyHandler), 0, NoAuth, []Middleware{}},
 		{1.1, http.MethodGet, `cdns/routing$`, handlerToFunc(proxyHandler), 0, NoAuth, []Middleware{}},