Soracom determines the final cost for an individual IoT SIM card's data usage by performing a specific sequence of calculations. This process involves measuring raw usage, converting it to billable data, and applying the appropriate plan rates.
1. Calculating Raw Data Usage
First, Soracom measures the total volume of data transmitted. It is important to note that this calculation includes not only the data payload but also the packet overhead required for transmission.
- Packet Overhead: The calculation includes Ethernet, IP, UDP, and GTP headers.
- Impact: These headers add approximately 50-54 bytes per packet to the total usage.
For a detailed technical breakdown of how these packets are measured, please refer to the Data Usage Calculation documentation.
Unit Conversion Note: Soracom calculates data sizes using binary prefixes, where 1,024 bytes = 1 KB, 1,024 KB = 1 MB, etc.
2. Determining Billable Data
Once the raw data usage is measured, it is converted into "billable data" based on the minimum billing unit associated with the country where the device is located.
- Rounding: Raw data usage is rounded up to the nearest increment of the minimum billing unit.
- Per-SIM Calculation: This rounding is applied to each SIM card individually. It is not calculated based on the aggregate usage across all SIM cards in an account.
To view the minimum billing units for specific countries, refer to the Supported Carriers documentation.
3. Applying Data Rates
After the billable data amount is established, Soracom applies charges based on the SIM card's subscription plan and the location of usage. The source for pricing information depends on the type of plan:
- Pay-As-You-Go Rates: For standard usage rates by country, refer to the Supported Carriers documentation.
- Bundled Plan Fees: For overage prices and fees associated with bundled data plans, refer to the Pricing and Fee Schedule.