diff --git a/package.json b/package.json
index 9e7a61e..ac11d22 100644
--- a/package.json
+++ b/package.json
@@ -32,6 +32,7 @@
     "@fastify/cors": "^8.2.0",
     "@supabase/supabase-js": "^2.0.5",
     "aws-sdk": "^2.1272.0",
+    "cron-parser": "^4.8.1",
     "date-fns": "^2.30.0",
     "dotenv": "^16.0.3",
     "fastify": "^4.10.2",
diff --git a/src/services/requests/scanService.ts b/src/services/requests/scanService.ts
index 340240c..ad5e62c 100644
--- a/src/services/requests/scanService.ts
+++ b/src/services/requests/scanService.ts
@@ -10,7 +10,7 @@ import { createReport } from "../../storage/report.storage";
 import { ScanDoesNotExist, UserHasNotEnoughCredits } from "../../exceptions/exceptions";
 import { deleteProbes, updateProbesByScanId } from "../../storage/probe.storage";
 import { getUserCredits, updateUserCredits } from "../../storage/credits.storage";
-import { probesPriceMapping } from "../../config";
+import { getAvailableProbes, probesPriceMapping } from "../../config";
 
 
 export const requestScan = async (scanRequest: CreateScanRequest): Promise<ScanRequestResponse> => {
@@ -19,7 +19,9 @@ export const requestScan = async (scanRequest: CreateScanRequest): Promise<ScanR
 
     const userCredits = await getUserCredits(scanRequest.user_id)
 
-    if (userCredits < scanRequest.probes?.length) {
+    const availableProbes = getAvailableProbes()
+    const sumOfCreditsToUse = scanRequest.probes?.reduce((sum, probe) => sum + availableProbes[probe.name]?.price, 0)
+    if (userCredits < sumOfCreditsToUse) {
         throw new UserHasNotEnoughCredits(scanRequest.user_id)
     }
 
@@ -69,7 +71,7 @@ export const requestScan = async (scanRequest: CreateScanRequest): Promise<ScanR
     console.log(`[REQUEST][${newScanId}] Published request to Queue !`)
 
     // Update user credits
-    await updateUserCredits(scanRequest.user_id, userCredits - scanRequest.probes?.length)
+    await updateUserCredits(scanRequest.user_id, { remainingCredits: userCredits - sumOfCreditsToUse })
 
     return { scanId: newScanId };
 }
@@ -134,7 +136,9 @@ export const updateScan = async (scanId: string, scanWithProbes: UpdateScanReque
 export const restartScan = async (scan: ScanWithProbes): Promise<void> => {
     console.log(`[REQUEST][SCAN][RESTART][${scan.id}] Restarting scan...`)
     const userCredits = await getUserCredits(scan.userId)
-    if (userCredits < scan.probes?.length) {
+    const availableProbes = getAvailableProbes()
+    const sumOfCreditsToUse = scan.probes?.reduce((sum, probe) => sum + availableProbes[probe.name]?.price, 0)
+    if (userCredits < sumOfCreditsToUse) {
         throw new UserHasNotEnoughCredits(scan.userId)
     }
 
@@ -156,5 +160,5 @@ export const restartScan = async (scan: ScanWithProbes): Promise<void> => {
     console.log(`[REQUEST][SCAN][RESTART][${scan.id}] Published request to Queue !`)
 
     // Update user credits
-    await updateUserCredits(scan.userId, userCredits - scan.probes?.length)
+    await updateUserCredits(scan.userId, { remainingCredits: userCredits - sumOfCreditsToUse })
 }
\ No newline at end of file
diff --git a/src/storage/credits.storage.ts b/src/storage/credits.storage.ts
index c328148..ca88575 100644
--- a/src/storage/credits.storage.ts
+++ b/src/storage/credits.storage.ts
@@ -2,7 +2,7 @@ import { UserCredits } from "../models/credit"
 import supabaseClient from "./supabase"
 
 export const getUserCredits = async (userId: string): Promise<number> => {
-    return (await supabaseClient.from('user_credits').select('remaningCredits').eq('userId', userId).maybeSingle()).data?.remaningCredits || 0
+    return (await supabaseClient.from('user_credits').select('remainingCredits').eq('userId', userId).maybeSingle()).data?.remainingCredits || 0
 }
 
 export const updateUserCredits = async (userId: string, payload: Partial<UserCredits>): Promise<void> => {
diff --git a/src/utils/probe.utils.ts b/src/utils/probe.utils.ts
new file mode 100644
index 0000000..af78fd9
--- /dev/null
+++ b/src/utils/probe.utils.ts
@@ -0,0 +1,32 @@
+import cronParser from 'cron-parser'
+import { isAfter, addMonths } from 'date-fns'
+import { Probe } from '../models/probe'
+
+export const calculateCreditUsageForPeriod = (periodicity: string, renewalDate: Date, nbCreditsForProbe): number => {
+    if (!periodicity) {
+        return 0
+    }
+
+    if (periodicity === 'ONCE') {
+        return nbCreditsForProbe
+    }
+
+    // Protection against infinite loop
+    let iteration = 0
+
+    const occurrences = []
+    const interval = cronParser.parseExpression(periodicity)
+    while (interval.hasNext() && iteration < 100) {
+        const occurrence = interval.next()
+        if (isAfter(occurrence.toDate(), renewalDate)) {
+            break;
+        }
+        occurrences.push(occurrence)
+        iteration++
+    }
+    return occurrences.length * nbCreditsForProbe
+}
+
+export const getAllCreditsUsedByProbesForMonth = (probes: Probe[], periodicity: string): number => {
+    return probes?.reduce((sum, probe) => sum + calculateCreditUsageForPeriod(periodicity, addMonths(new Date(), 1), probe.price), 0) || 0
+} 
\ No newline at end of file
diff --git a/yarn.lock b/yarn.lock
index 0473d6c..5d266cc 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1361,6 +1361,13 @@ cookie@^0.5.0:
   resolved "https://registry.yarnpkg.com/cookie/-/cookie-0.5.0.tgz#d1f5d71adec6558c58f389987c366aa47e994f8b"
   integrity sha512-YZ3GUyn/o8gfKJlnlX7g7xq4gyO6OSuhGPKaaGssGB2qgDUS0gPgtTvoyZLTt9Ab6dC4hfc9dV5arkvc/OCmrw==
 
+cron-parser@^4.8.1:
+  version "4.8.1"
+  resolved "https://registry.yarnpkg.com/cron-parser/-/cron-parser-4.8.1.tgz#47062ea63d21d78c10ddedb08ea4c5b6fc2750fb"
+  integrity sha512-jbokKWGcyU4gl6jAfX97E1gDpY12DJ1cLJZmoDzaAln/shZ+S3KBFBuA2Q6WeUN4gJf/8klnV1EfvhA2lK5IRQ==
+  dependencies:
+    luxon "^3.2.1"
+
 cross-fetch@^3.1.5:
   version "3.1.5"
   resolved "https://registry.yarnpkg.com/cross-fetch/-/cross-fetch-3.1.5.tgz#e1389f44d9e7ba767907f7af8454787952ab534f"
@@ -2524,6 +2531,11 @@ lru-cache@^6.0.0:
   dependencies:
     yallist "^4.0.0"
 
+luxon@^3.2.1:
+  version "3.3.0"
+  resolved "https://registry.yarnpkg.com/luxon/-/luxon-3.3.0.tgz#d73ab5b5d2b49a461c47cedbc7e73309b4805b48"
+  integrity sha512-An0UCfG/rSiqtAIiBPO0Y9/zAnHUZxAMiCpTd5h2smgsj7GGmcenvrvww2cqNA8/4A5ZrD1gJpHN2mIHZQF+Mg==
+
 make-dir@^3.0.0:
   version "3.1.0"
   resolved "https://registry.yarnpkg.com/make-dir/-/make-dir-3.1.0.tgz#415e967046b3a7f1d185277d84aa58203726a13f"