Two separate things get called bandwidth. Keep them apart.
Port speed is per server
How fast a server can move traffic at any instant.
- General Compute (
gc.*): 2.5 Gbps - Network Optimized (
no.*): 10 Gbps
Port speed is a property of the plan and cannot be changed without resizing to a plan that has it.
Transfer is per account
How much total traffic you move in a period. Every account receives 2 TB of free transfer at the start of each UTC calendar month. Each VPS also earns up to 500 GB of instance credits per month, shared across the same pool. These are transfer credits measured in GB or TB, separate from your money balance.
How instance credits accrue
Instance credits are earned in proportion to how long the VPS has been provisioned during the UTC calendar month:
500 GB × time provisioned this month ÷ total time in this calendar month
A VPS provisioned for 15 days of a 30-day month earns 250 GB. If it stays provisioned for the whole month, it earns 500 GB. A newly deployed VPS starts earning when provisioning completes; it does not receive the full 500 GB immediately. The calculation uses elapsed time, including partial days.
Stopped and suspended VPS instances keep earning instance credits because their resources remain reserved. Requesting destruction stops new credits; the credits it already earned stay in your account pool until the next monthly reset. Unused free and instance credits do not roll over.
The pool is shared across all your servers. Resizing a VPS does not increase its 500 GB monthly earning rate, and a plan's published bandwidth figure is not a separate transfer cap.
Buying more
Prepaid blocks are $3.00 per TB per calendar month, added to the pool from Billing. Bought mid-month, you pay only for the days left (including today) and still get the full extra TB for this month's pool. A block auto-renews on the 1st at the full monthly rate until you turn renewal off, and you get an email a few days before it does.
Overage on traffic past the pool is the same $3.00 per TB, calculated and posted to account credit in batches. From Billing → Add bandwidth you can disable automatic overage billing. If transfer then exceeds the pool, servers are suspended instead of charging. They resume when the pool resets, when newly earned instance credits cover the usage, or when you add enough prepaid bandwidth to cover the overage. You can also turn automatic overage billing back on. This does not suspend the account for non-payment and does not start a termination review.
Blocks and overage cost the same per TB. Add a block when you want the extra capacity in the pool up front, including mid-month, when the charge is prorated, or when automatic overage billing is off.
Resize for CPU, buy transfer for traffic
Moving to a bigger plan does not buy you a bigger pool. Each VPS earns up to 500 GB per month over time. Buy blocks when you need more transfer available immediately.
Where to look
Networking → Bandwidth usage is the account transfer page. The Bandwidth pool chart separates free credits, instance credits earned so far, purchased blocks, and potential credits by the end of the month. The usage bar shows transfer already consumed. Potential credits depend on your current VPS instances remaining provisioned through month-end; they are not available to spend yet. The same page lists each source in the pool and each VPS's contribution.
Billing → Bandwidth is where you buy blocks and set overage billing. Each server's Usage Graphs tab shows that server's share of the pool this month (inbound, outbound, and total).
The same figures are on the API: GET /api/v1/account for the pool plus every
server's share this month, and GET /api/v1/servers/<id>/bandwidth for one
server including previous months. See API recipes.