DCI Bandwidth Calculator
Size a data centre interconnect from daily change rate, replication window, RPO and distance latency.
About DCI Bandwidth Calculator
Replication bandwidth is the changed data divided by the window it must fit into, reduced by compression and then inflated by how peaky the change rate is. Distance sets a floor on latency that no amount of bandwidth fixes, which is what rules synchronous replication in or out beyond roughly 100 km. DCI circuits are the most expensive links a business buys, and RPO commitments are contractual — both depend on this figure being right rather than optimistic.
Formula
DCI Bandwidth
sustained Mbps = change GB × 8000 ÷ window seconds × (1 − reduction); required = sustained × peak factor; RTT ms ≈ distance km × 0.01.
- change GB × 8000
- Gigabytes converted to megabits
- 0.01 ms/km
- Round-trip fibre delay — 5 µs per km each way
Worked example
With the default values below, DCI Bandwidth Calculator returns DCI Bandwidth Required of 311.11. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Daily data changeaccepts 0.1–10,000,000 GB
- 800 GB
- Replication windowaccepts 0.1–24 hours
- 8 hours
- Recovery point objectiveaccepts 0–1,440 minutes
- 15 minutes
- Reduction from compression and dedupaccepts 0–95 %
- 30 %
- Peak-to-average factoraccepts 1–10 x
- 2 x
- Distance between sitesaccepts 1–20,000 km
- 600 km
Results
- DCI Bandwidth Required
- 311.11 Mbps
- Sustained Rate
- 155.56 Mbps
- Rate Needed to Hold the RPO
- 51.85 Mbps
- Round-trip Latency
- 6.00 ms
- Replication Mode Feasible
- Synchronous possible but latency-sensitive
Step by step
- 1Values used
- 2DCI Bandwidth
- 3DCI Bandwidth Required= 311.11 Mbps
- 4Sustained Rate= 155.56 Mbps
- 5Rate Needed to Hold the RPO= 51.85 Mbps
- 6Round-trip Latency= 6.00 ms
- 7Replication Mode Feasible= Synchronous possible but latency-sensitive
Assumptions and limits
- The result is derived only from the 6 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is DCI Bandwidth calculated?
sustained Mbps = change GB × 8000 ÷ window seconds × (1 − reduction); required = sustained × peak factor; RTT ms ≈ distance km × 0.01. Replication bandwidth is the changed data divided by the window it must fit into, reduced by compression and then inflated by how peaky the change rate is. Distance sets a floor on latency that no amount of bandwidth fixes, which is what rules synchronous replication in or out beyond roughly 100 km.
Why does DCI Bandwidth matter?
DCI circuits are the most expensive links a business buys, and RPO commitments are contractual — both depend on this figure being right rather than optimistic.
What values do I need to enter?
This calculator takes 6 inputs: Daily data change, Replication window, Recovery point objective, Reduction from compression and dedup, Peak-to-average factor, Distance between sites. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.