# Monthly tracked users (MTUs) billing guide Learn about how Amplitude bills with Monthly Tracked Users. Source: https://amplitude.com/docs/admin/billing-use/mtu-guide --- On this page - [Track your MTUs](#track-your-mtus) - [Estimate your MTUs](#estimate-your-mtus) - [View your MTU use](#view-your-mtu-use) - [Discrepancies with counts provided by other tools](#discrepancies-with-counts-provided-by-other-tools) - [MTU limits](#mtu-limits) - [Calculate your organization’s limit of events per MTU](#calculate-your-organizations-limit-of-events-per-mtu) - [Exceeding limits on a free plan](#exceeding-limits-on-a-free-plan) - [Unexpected usage spikes](#unexpected-usage-spikes) - [How Amplitude counts backfilled events](#how-amplitude-counts-backfilled-events) - [Drop filters and MTUs](#drop-filters-and-mtus) # Monthly tracked users (MTUs) billing guide An MTU is a unique user who triggers one or more events within a calendar month. Amplitude tracks anonymous users with device ID and identified users with user ID. If a user appears in two or more projects, they still count as a single MTU. Amplitude tracks anonymous users as distinct MTUs, even if they visited before while logged in. If an anonymous user later logs into the site, Amplitude merges all events triggered while the user was anonymous under their user ID. The merged user counts as a single MTU. Amplitude calculates MTU usage daily, with one final calculation after the end of the calendar month to accommodate late-arriving events. After the final calculation, Amplitude no longer updates the MTU count to reflect later user merges caused by identify calls on anonymous users. Your MTU count doesn't increase due to user mapping, identify calls, or group identifies. All Amplitude plans support MTU-based pricing. Customers who use sampling aren't eligible for MTU-based pricing. Events that don't count toward MTUs `[Experiment] Exposure` and `[Experiment] Assignment` events don't count toward your organization's MTU count. Amplitude uses these events for experiment analysis and monitoring but they don't affect your billing. ## Track your MTUs The first step in setting up MTU tracking is to understand [how Amplitude tracks unique users](/docs/data/sources/instrument-track-unique-users). The best way to ensure accurate counting of MTUs is to support a one-to-one correlation between user IDs and actual users. If you're using test data and generating fictitious user IDs for testing, each test user is also included in your MTU count. ### Estimate your MTUs If you haven't implemented tracking yet, you can use your monthly active user (MAU) count to estimate your current MTU usage. These counts are usually similar if they account for anonymous visitors identically. ## View your MTU use To view your MTU usage, navigate to *Settings > Organization Settings > Plans & Billing*. MTU statistics are visible in their own panel. MTU counts aren't available for every plan type. Sometimes, a single user may count **multiple times** when totaling MTUs. This can happen when users log in on their usual device, then later open the app anonymously on a different device or platform. Because Amplitude can't connect these two users, they register as distinct MTUs unless the user eventually logs in on all devices. At that point, Amplitude merges their profiles into a single user. It can also happen if a user has two unlinked user IDs and uses both of them in a single month. User actions can also result in a **reduced** MTU count. If a user interacts with your app anonymously and then later logs into their account on that same device, Amplitude merges the anonymous usage with the logged-in usage. The merged usage results in a single MTU. MTU billing uses UTC time. Go to [Investigate your organization's MTU usage in the Amplitude Community](https://community.amplitude.com/building-and-sharing-your-analysis-58/learn-how-to-investigate-your-org-s-monthly-tracked-users-mtus-2163). ### Discrepancies with counts provided by other tools No two tools work exactly the same way or under the exact same conditions. Most tools ingest and process data differently, which generates different results. Your MTU count can also differ from the results generated by running a user count query within Amplitude because MTU calculations use different logic. If you believe there is an error in your MTU count, contact [Amplitude support](http://support.amplitude.com). ## MTU limits MTU limits are defined by your organization's plan or the MTU volume you purchased. Amplitude determines whether you owe overage fees based on: - Your total MTU volume. - Your events per MTU volume. Amplitude calculates each limit on the last day of each calendar month. Exceeding either limit can result in overage charges. Amplitude alerts you when you are approaching your limit so you can avoid exceeding it. ### Calculate your organization’s limit of events per MTU Your organization's limit of events per MTU depends on your Amplitude plan. For organizations on the Starter plan, this limit is 1,000 events per MTU. Amplitude calculates billing based on **total MTU count**. Most of the time, your total MTU count is equal to your **unique MTU count**, which is the number of unique IDs associated with any tracked event triggered this month. If you exceed your monthly limit, Amplitude adds **synthetic MTUs** to your monthly MTU count. Use this formula to calculate your organization's synthetic MTU count: `(Events tracked this month - (Your plan's monthly MTU limit x 1,000)) / 1,000` This works out to one synthetic MTU for every 1,000 events over your plan's quota allotment. To calculate your total MTU count for the month, add your unique MTU count to your synthetic MTU count. ### Exceeding limits on a free plan If you're a non-paying customer, Amplitude blocks your account when you exceed your monthly MTU limit **three times**. You lose access to your charts and dashboards, but you keep access to certain admin functions, like the User API, so you can meet compliance obligations. Amplitude continues to ingest data **up to and over** your limit. Unless you upgrade to a paid plan, you can't access that data. If you continue to exceed your monthly limit without upgrading, Amplitude deletes your account six months after it's first blocked. ## Unexpected usage spikes Large and sudden increases in MTUs are almost always tied to spikes in product usage. If your company recently launched a new marketing campaign, a significant product update, or an instrumentation change, that may explain the spike. MTUs may also increase unexpectedly when you add new event sources that result in either more users, or more events for users active in third-party tools but not necessarily in your product (for example, adding an email platform as a data source). If you believe your MTUs have spiked in error, contact [Amplitude support](http://support.amplitude.com). ## How Amplitude counts backfilled events When you add backdated events for previous months, Amplitude adds one MTU for each month in which a distinct user appears. Amplitude bases MTU usage calculations on the month you add an event to Amplitude. If you backfill data from previous months in February, for example, Amplitude counts all backfilled usage against February’s MTU quota. Similarly, determining whether a user is unique depends on the month they trigger the event. For example, if Amplitude records three events for a single user, with one dated today, one dated one month ago, and one dated two months ago, the count is one unique MTU in the current month. Because of this, backfilling data is a common cause of spikes in MTU usage. ## Drop filters and MTUs When you use a [drop filter](/docs/data/remove-invalid-data), Amplitude excludes a set of ingested events from your chart based on the criteria you set. Your query doesn't return these events, but the events still exist because Amplitude doesn't delete them. Because of this, the number of uniques on a drop-filtered chart in Amplitude Analytics may not match the number of uniques on the MTU chart in your billing report. Was this helpful?