Get This Month’s AWS CloudWatch Cost With Cost Explorer

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "ReadCloudWatchCostMonthToDate",
      "Effect": "Allow",
      "Action": [
        "ce:GetDimensionValues",
        "ce:GetCostAndUsage"
      ],
      "Resource": "*"
    }
  ]
}

// cloudwatch-cost-this-month.ts
// Month-to-date Amazon CloudWatch cost, split by usage type, from Cost Explorer.
// Makes 2 Cost Explorer API requests (more if results are paginated); each costs $0.01.
// Usage: npx tsx cloudwatch-cost-this-month.ts
import {
  CostExplorerClient,
  GetCostAndUsageCommand,
  GetDimensionValuesCommand,
  type GetCostAndUsageCommandOutput,
} from "@aws-sdk/client-cost-explorer";

const iso = (d: Date) => d.toISOString().slice(0, 10);

async function main(): Promise<void> {
  // Cost Explorer uses UTC dates and an exclusive End date, so this covers
  // the 1st of the month through yesterday (today's data is still arriving).
  const now = new Date();
  const start = new Date(Date.UTC(now.getUTCFullYear(), now.getUTCMonth(), 1));
  const today = new Date(Date.UTC(now.getUTCFullYear(), now.getUTCMonth(), now.getUTCDate()));
  if (today.getTime() === start.getTime()) {
    console.log("It is the 1st of the month (UTC): there is no complete day to report yet.");
    return;
  }
  const period = { Start: iso(start), End: iso(today) };
  const ce = new CostExplorerClient({ region: "us-east-1" });

  // 1. Find the exact SERVICE value(s) Cost Explorer uses for CloudWatch in this period.
  const dims = await ce.send(
    new GetDimensionValuesCommand({
      TimePeriod: period,
      Dimension: "SERVICE",
      SearchString: "CloudWatch",
      Context: "COST_AND_USAGE",
    }),
  );
  let requests = 1;
  const services = (dims.DimensionValues ?? [])
    .map((d) => d.Value)
    .filter((v): v is string => typeof v === "string" && v.length > 0);
  if (services.length === 0) {
    console.log(`No CloudWatch charges between ${period.Start} and ${period.End}.`);
    return;
  }

  // 2. Month-to-date cost for those services, grouped by usage type.
  const byUsageType = new Map<string, number>();
  let nextPageToken: string | undefined;
  do {
    const res: GetCostAndUsageCommandOutput = await ce.send(
      new GetCostAndUsageCommand({
        TimePeriod: period,
        Granularity: "MONTHLY",
        Metrics: ["UnblendedCost"],
        Filter: { Dimensions: { Key: "SERVICE", Values: services } },
        GroupBy: [{ Type: "DIMENSION", Key: "USAGE_TYPE" }],
        NextPageToken: nextPageToken,
      }),
    );
    requests++;
    for (const result of res.ResultsByTime ?? []) {
      for (const group of result.Groups ?? []) {
        const usageType = group.Keys?.[0] ?? "(unknown)";
        const amount = Number(group.Metrics?.UnblendedCost?.Amount ?? 0);
        byUsageType.set(usageType, (byUsageType.get(usageType) ?? 0) + amount);
      }
    }
    nextPageToken = res.NextPageToken;
  } while (nextPageToken);

  const rows = [...byUsageType.entries()].sort((a, b) => b[1] - a[1]);
  const total = rows.reduce((s, [, amount]) => s + amount, 0);

  // A straight-line projection: average daily cost so far x days in the month.
  const daysElapsed = Math.round((today.getTime() - start.getTime()) / 86_400_000);
  const daysInMonth = new Date(Date.UTC(now.getUTCFullYear(), now.getUTCMonth() + 1, 0)).getUTCDate();
  const projected = (total / daysElapsed) * daysInMonth;

  console.log(`CloudWatch cost (${services.join(", ")}), ${period.Start} to ${period.End} (exclusive)`);
  console.table(
    rows
      .filter(([, amount]) => Math.abs(amount) >= 0.005)
      .map(([usageType, amount]) => ({ "Usage type": usageType, Cost: amount.toFixed(2) })),
  );
  console.log(`Month to date: ${total.toFixed(2)} USD over ${daysElapsed} days`);
  console.log(`Straight-line projection for the month: ${projected.toFixed(2)} USD`);
  console.log(`Cost Explorer API requests made: ${requests} (about $${(requests * 0.01).toFixed(2)})`);
}

main().catch((err) => {
  console.error(err);
  process.exit(1);
});

npm install @aws-sdk/client-cost-explorer
npm install --save-dev tsx typescript

AWS_PROFILE=billing-readonly npx tsx cloudwatch-cost-this-month.ts

CloudWatch cost (AmazonCloudWatch), 2026-09-01 to 2026-09-27 (exclusive)
┌─────────┬──────────────────────────────┬─────────┐
│ (index) │ Usage type                   │ Cost    │
├─────────┼──────────────────────────────┼─────────┤
│ 0       │ 'DataProcessing-Bytes'       │ '38.61' │
│ 1       │ 'CW:MetricMonitorUsage'      │ '14.40' │
│ 2       │ 'TimedStorage-ByteHrs'       │ '6.92'  │
│ 3       │ 'CW:GMD-Metrics'             │ '3.18'  │
│ 4       │ 'CW:AlarmMonitorUsage'       │ '2.50'  │
│ 5       │ 'EU-DataProcessing-Bytes'    │ '1.87'  │
│ 6       │ 'CW:Requests'                │ '0.42'  │
└─────────┴──────────────────────────────┴─────────┘
Month to date: 67.90 USD over 26 days
Straight-line projection for the month: 78.35 USD
Cost Explorer API requests made: 2 (about $0.02)