What Is CTP (Capable to Promise)?
Also known as: capable to promise, CTP check
Definition
CTP (capable to promise) is an order promising method that goes beyond available inventory by simulating whether required material and work center capacity can be obtained in time, returning a delivery date the plant can actually achieve.
CTP (Capable to Promise) Explained
Where ATP asks what is already available, CTP asks what could be made available. The check runs a simulated finite-capacity plan for the requested quantity: it explodes the bill of materials, verifies or plans component availability using supplier lead times, walks the routing to find open capacity at each work center, and returns the earliest completion date consistent with both constraints. Some implementations also reserve the simulated capacity so the promise is not consumed by the next quote before the order is confirmed.
CTP requires substantially better data than ATP. Routings must carry realistic setup and run times, work center calendars must reflect actual shifts and planned downtime, and supplier lead times must be trustworthy. If any of these are approximations, CTP produces precise-looking dates that are no more reliable than the guess it replaced, with the added risk that the sales team now trusts them. This is why most implementations phase CTP in only after routing and calendar data has been cleaned.
In engineer-to-order and configure-to-order environments CTP is more valuable and more difficult. Configured products may not have a fixed bill of materials or routing until the configuration is resolved, so the promising engine must work from a configurator-generated structure or a representative model. Aerospace and defense shops often use a hybrid: CTP against the constrained bottleneck operations only, with standard lead time offsets for the rest, which captures most of the accuracy at a fraction of the modeling effort.
The practical trade-off is response time. A full CTP simulation across a busy plant can take seconds to minutes, which is uncomfortable inside an order entry conversation. Vendors address this with cached capacity buckets, background simulation, or promising against a pre-calculated constrained supply picture. Understand which approach your ERP uses, because a cached model that refreshes nightly will not reflect the three orders promised this morning.
Why It Matters
- CTP lets sales quote aggressive dates on constrained products without gambling on whether the plant can deliver.
- It surfaces bottleneck saturation at the moment of quoting, when the commercial team can still trade price for a later date.
- CTP accuracy is entirely dependent on routing and calendar data, so it doubles as a forcing function for master data quality.
- In make-to-order and engineer-to-order work, where finished inventory does not exist, CTP is the only meaningful promising method.
In Practice
Common gotcha: CTP is enabled while work center calendars still show 24 hours of availability seven days a week from the demo configuration. The engine then finds capacity on Saturday night at 2 a.m. and returns dates the plant cannot hit. Validate shift calendars, holidays, and planned maintenance downtime before turning CTP on for any live order entry.
Frequently Asked Questions
When should a manufacturer use CTP instead of ATP?
Use CTP when finished inventory rarely exists to promise from, which is typical in make-to-order, engineer-to-order, and highly configured products. Also use it when a known bottleneck determines delivery, since ATP will happily promise dates the constrained work center cannot support. For stocked, high-volume standard items, ATP is faster and sufficient.
What data quality does CTP require?
At minimum: accurate routings with realistic setup and run times, work center calendars reflecting true shift patterns and downtime, valid supplier lead times for purchased components, and complete bills of materials for the configurations being quoted. Weakness in any one of these produces dates that look authoritative but fail in execution.
Related Terms
ATP (Available to Promise)
ATP (available to promise) is the portion of inventory and scheduled production not yet committed to existing customer orders, calculated by date so order entry can quote a delivery a customer can rely on.
Capacity Planning
Capacity planning is the process of comparing the labor and machine hours a production plan requires against the hours each work center actually has available, identifying overloads early enough to reschedule, add shifts, or outsource.
Routing
A routing is the ERP record that defines the ordered sequence of operations required to manufacture an item, specifying for each step the work center or machine, setup time, run time per unit, move and queue time, and any outside processing.
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