diff --git a/services/web/scripts/add_user_count_to_csv.js b/services/web/scripts/add_user_count_to_csv.js
new file mode 100644
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+++ b/services/web/scripts/add_user_count_to_csv.js
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+// Usage: node scripts/add_user_count_to_csv.js [OPTS] [INPUT-FILE]
+// Looks up the number of users for each domain in the input csv file and adds
+// columns for the number of users in the domain, subdomains, and total.
+const fs = require('fs')
+const csv = require('csv/sync')
+const minimist = require('minimist')
+const UserGetter = require('../app/src/Features/User/UserGetter')
+const { db, waitForDb } = require('../app/src/infrastructure/mongodb')
+const _ = require('lodash')
+
+const argv = minimist(process.argv.slice(2), {
+  string: ['domain', 'output'],
+  boolean: ['help'],
+  alias: {
+    domain: 'd',
+    output: 'o',
+  },
+  default: {
+    domain: 'Email domain',
+    output: '/dev/stdout',
+  },
+})
+
+if (argv.help || argv._.length > 1) {
+  console.error(`Usage: node scripts/add_user_count_to_csv.js [OPTS] [INPUT-FILE]
+    Looks up the number of users for each domain in the input file and adds
+    columns for the number of users in the domain, subdomains, and total.
+
+    Options:
+
+        --domain    name of the csv column containing the email domain (default: "Email domain")
+        --output    output file (default: /dev/stdout)
+    `)
+  process.exit(1)
+}
+
+const input = fs.readFileSync(argv._[0], 'utf8')
+const records = csv.parse(input, { columns: true })
+
+if (records.length === 0) {
+  console.error('No records in input file')
+  process.exit(1)
+}
+
+async function main() {
+  await waitForDb()
+  for (const record of records) {
+    const domain = record[argv.domain]
+    const { domainUserCount, subdomainUserCount } = await getUserCount(domain, {
+      _id: 1,
+    })
+    record['Domain Users'] = domainUserCount
+    record['Subdomain Users'] = subdomainUserCount
+    record['Total Users'] = domainUserCount + subdomainUserCount
+  }
+  const output = csv.stringify(records, { header: true })
+  fs.writeFileSync(argv.output, output)
+}
+
+async function getUserCount(domain) {
+  const domainUsers = await UserGetter.promises.getUsersByHostname(domain, {
+    _id: 1,
+  })
+  const subdomainUsers = await getUsersByHostnameWithSubdomain(domain, {
+    _id: 1,
+  })
+  return {
+    domainUserCount: domainUsers.length,
+    subdomainUserCount: subdomainUsers.length,
+  }
+}
+
+async function getUsersByHostnameWithSubdomain(domain, projection) {
+  const reversedDomain = domain.trim().split('').reverse().join('')
+  const reversedDomainRegex = _.escapeRegExp(reversedDomain)
+  const query = {
+    emails: { $exists: true },
+    // look for users in subdomains of a domain, but not the domain itself
+    // e.g. for domain 'foo.edu', match 'cs.foo.edu' but not 'foo.edu'
+    // we use the reversed hostname index to do this efficiently
+    // we need to escape the domain name to prevent '.' from matching any character
+    'emails.reversedHostname': { $regex: '^' + reversedDomainRegex + '\\.' },
+  }
+  return await db.users.find(query, { projection }).toArray()
+}
+
+main()
+  .then(() => {
+    console.error('Done')
+    process.exit(0)
+  })
+  .catch(err => {
+    console.error(err)
+    process.exit(1)
+  })