A package tracking API may charge by request, tracked shipment, or a combination of subscription and usage. Those units are not interchangeable. A single package that is checked repeatedly might count as one tracked shipment on one service and dozens of API requests on another.
To build a useful estimate, start with how your application will actually monitor packages. This guide uses C2W’s published request-based plans as a worked example; the same workload-first method applies when evaluating other providers.
1. Count the shipments being monitored at the same time
Use your active shipment count, not just the number of labels created today. Packages often remain in transit for several days, so older shipments overlap with new ones.
If you do not yet have a count, estimate average active shipments as:
Shipments started per day × average days monitored = average active shipments
For example, a business starting 80 shipments a day and monitoring each for an average of five days may have roughly 400 active shipments at a time. Plan separately for seasonal peaks, weekends, and delayed shipments that remain open longer than usual.
2. Choose a realistic check frequency
Next, estimate how often your system will request an update for each active package. The right interval depends on the customer experience and operations workflow you need. More calls do not guarantee more carrier scans or fresher source data.
For example, checking 400 active packages four times a day creates a baseline of 1,600 API requests per day. Checking those same packages once daily creates 400. Record the schedule you actually intend to run, including whether it changes near the expected delivery date or after an exception.
3. Add retries, manual refreshes, and other calls
The baseline is rarely the whole budget. Include retries after temporary failures, support-team lookups, customer-initiated refreshes, and any scheduled reconciliation jobs.
A simple estimate is:
Daily requests = active shipments × checks per shipment per day + expected retries and manual refreshes
If 500 active shipments are checked four times daily, the baseline is 2,000 requests. A 5% allowance for retries and manual lookups adds about 100, for a planning estimate of 2,100 requests per day. Use your own observed failure and support patterns when available.
Retries should be bounded and spaced out. Aggressive retry loops can increase cost while making rate-limit problems worse. C2W’s public reference documents one tracking number per request; confirm batch endpoints and quota accounting with C2W before assuming that batching changes the request count.
4. Compare the busiest day with plan limits
C2W’s published plans are measured in API requests per day. The pricing page lists these tiers, verified on September 11, 2026:
| Plan | Monthly price | Requests per day | Overage |
|---|---|---|---|
| Basic | $0 | 5 | Hard limit |
| Pro | $9.99 | 150 | Hard limit |
| Ultra | $29.99 | 700 | Hard limit |
| Mega | $89.99 | 2,500 | $0.0008 per additional request |
Daily allowances are not pooled into monthly credits. A plan’s per-second rate limit is separate from its daily allowance: being under the daily total does not mean you can send every request at once. Check the current pricing and request-budget page and your RapidAPI subscription before subscribing, since prices and billing terms can change.
Worked examples
The following examples use four checks per active shipment per day and exclude retries unless noted. They compare each workload with the listed daily allowances rather than treating those limits as monthly pools.
| Active shipments | Checks each per day | Baseline requests per day | Example plan fit |
|---|---|---|---|
| 25 | 4 | 100 | Pro: 50 requests of headroom |
| 100 | 4 | 400 | Ultra: 300 requests of headroom |
| 500 | 4 | 2,000 | Mega: 500 requests of headroom |
| 3,000 | 4 | 12,000 | Mega plus overage or a custom plan |
At 3,000 active shipments, 12,000 requests per day would exceed Mega’s 2,500-request allowance by 9,500. At the listed $0.0008 per additional request, that is $7.60 in overage per day. Across 30 identical days, the arithmetic estimate is $89.99 + (30 × $7.60) = $317.99.
This is an illustration using the listed overage rate, not a quote. Actual billing depends on the current plan terms, account counters, daily usage, and taxes. If you expect this volume, compare a custom arrangement as well.
5. Convert daily usage into a monthly forecast carefully
Multiplying a stable daily workload by the number of operating days helps estimate total calls. For instance, 400 calls a day over 30 days is 12,000 monthly calls. But do not compare that total to a daily allowance as if the allowance were a monthly bucket. A 400-request day must fit the plan’s daily limit on that day.
For a request-priced estimate, separate the fixed subscription cost from billable overage:
Estimated monthly cost = monthly plan fee + sum of daily billable excess requests × overage rate
For a provider charging per tracked shipment, calculate the number of unique shipments and the provider’s included update behavior instead. Ask what counts as a shipment, whether repeated lookups are included, what happens after plan limits, and whether retries or manual refreshes consume additional credits.
6. Account for limits and engineering costs
A low API price is only one part of the total cost. Also consider:
- Carrier coverage: verify the exact services and routes your shipments use.
- Update model: polling creates recurring requests; webhook-based services may price or limit usage differently.
- Rate limits: spread scheduled requests over time and check peak throughput.
- Customer experience: include the engineering cost of dashboards, notifications, or tracking pages if the provider does not supply them.
- Operations: budget for monitoring, retries, exception handling, and support workflows.
- Seasonality: size for your busiest days and weeks, not just the annual average.
If you rely on event-driven notifications, note that C2W does not currently support webhooks; your application requests tracking updates. Compare providers using the same carrier mix and workload in our tracking API comparisons.
Make the estimate more accurate with a short pilot
Before committing to a plan, run a representative pilot. Track active shipments, API calls per package, retries, daily peaks, carrier mix, and how long shipments stay under monitoring. Test normal in-transit packages as well as delivered, delayed, and exception cases.
After a week or two, calculate the median day and the busiest day separately. The median helps with a typical budget; the peak shows whether daily limits or rate limits could interrupt service. Leave room for growth and avoid treating an estimate as a guarantee.
For a deeper look at request planning, see the C2W request-budget examples and the integration guide’s polling recommendations. If you are building exception workflows, the delivery-exception monitoring guide shows how tracking data can support operational review.
Frequently asked questions
Is one tracking number equal to one API request?
Not necessarily across all providers. In C2W’s public request-based model, each call counts as a request, so repeatedly checking one tracking number can use multiple requests. Ask other providers how they define a billable shipment or tracking unit.
Should I count all packages created this month?
Count the packages that are actively monitored on each day. A package may generate calls across multiple days, and shipments started earlier may overlap with new ones.
Can I reduce cost by checking less often?
Fewer checks generally reduce request usage, but choose an interval that meets your operational needs. More frequent polling does not guarantee that a carrier has published a new event.
Does C2W have a monthly request pool?
The published C2W plans list daily request allowances, not pooled monthly credits. Check the current pricing page and subscription dashboard for applicable limits and billing counters.