Data Transfer Cost Calculator — Egress Billing Per GB

Background.

Data transfer is the line on a cloud bill that surprises people, because it is the only one that scales with how popular you are rather than with what you provisioned. This calculator prices a month of it from four numbers you control: how much data left your network, how much of that was free, what you pay per gigabyte above the allowance, and how long the billing month is. It returns the bill, the billable volume, what the free allowance was actually worth, the blended rate across your whole volume, a flat-volume annual projection, and the average sustained bit rate the traffic implies.

No provider's prices are baked into this page, and that is deliberate. Egress rates change without notice, differ by region, by destination and by commitment, and any figure hard-coded into a calculator is wrong within months. What is fixed here is the shape of the model — a free allowance, then a rate per gigabyte above it — which is the structure almost every provider uses. Two allowance figures were confirmed from primary sources and are quoted below because they show how far apart providers sit: AWS publishes 100 GB of free data transfer out to the internet each month, aggregated across all its services and regions except China and GovCloud, while Google Cloud's free tier publishes 1 GB of outbound transfer from North America per month, excluding China and Australia. Two orders of magnitude between two major providers is exactly why the allowance is a field and not a constant.

The unit selector is the part most likely to change your answer without you noticing. A gigabyte in the decimal sense is 10⁹ bytes; a gibibyte is 2³⁰ = 1,073,741,824 bytes. They differ by 7.4%, and at the terabyte scale the gap widens to 10%. Providers are not consistent about which one they mean by "GB" on an invoice, and monitoring tools frequently report one while the bill charges the other. This page normalises everything to decimal GB before applying the rate and tells you the normalised figure, so you can hold it against your invoice and find out which convention you are actually being billed under. If the two disagree by roughly 7%, you have your answer.

The blended cost per gigabyte is the output worth reading twice. At the defaults — 5,000 GB with a 100 GB allowance at 0.09 per GB — the bill is 441, but the effective rate across the whole 5,000 GB is 0.0882, not 0.09, because the free allowance is spread over everything. That gap shrinks as volume grows, which is the quiet reason free tiers stop mattering the moment you have real traffic: at 100,000 GB the same allowance moves the blended rate by a tenth of a percent.

The average sustained rate output connects this page back to capacity planning. Five thousand gigabytes a month spread evenly over thirty days is 15.43 Mbps — a small number that tempts people into buying a small link. Do not. Real traffic has a diurnal peak that typically runs several times the mean, and links must be sized to the peak. Use the bandwidth calculator for that, and treat this figure only as a sanity check that the volume and the link are in the same universe.

One scope limit stated plainly: this is a flat-rate model with a single free allowance. It does not implement graduated tier bands, committed-use discounts, private-connection rates, inter-region or inter-zone transfer, or per-request charges. For a tiered schedule, run the calculator once per band with the volume and rate for that band and add the results.

What is data transfer cost calculator?

Data transfer cost — usually called egress, bandwidth or data transfer out — is the charge a provider applies to data leaving its network toward the internet. It is billed per unit of volume, almost always per gigabyte, over a monthly billing cycle, and it is separate from the charge for the compute or storage that produced the data. Most providers bill outbound traffic and not inbound, which is why uploading a hundred gigabytes usually costs nothing while serving it back a hundred times is the largest line on the invoice. The typical schedule has three parts: a free allowance each month, a headline rate per gigabyte above that allowance, and often a set of graduated bands where the rate steps down at higher volumes. Some providers add per-request charges, different rates by destination region, and much lower rates over dedicated private interconnects. The unit is the perennial ambiguity: an invoice that says GB may mean 10⁹ bytes or 2³⁰ bytes, and the difference is 7.4%. This calculator implements the free-allowance-plus-flat-rate core of that model with every figure supplied by you, normalises volume to decimal gigabytes, and reports the blended rate you are really paying once the free allowance is spread across the whole month's traffic.

How to use this calculator.

1. 01Enter your monthly outbound volume and choose the unit it is reported in. If your monitoring tool says GiB, choose GiB — do not silently treat it as GB, because that understates the volume by 7.4%.
2. 02Enter the free allowance your plan includes, in decimal GB. Enter 0 if there is none. Check the wording: allowances are often aggregated across all services and regions rather than granted per service.
3. 03Enter your own current published rate per GB. The default is a round placeholder and is not any provider's price — look up your rate for your region and destination, because both change it.
4. 04Set the number of days in the billing cycle. This affects only the average sustained rate, not the bill.
5. 05Read the blended cost per GB alongside the headline rate to see what the free allowance is actually worth to you at your volume.
6. 06For a tiered price schedule, run the calculator once per band — volume in that band, rate for that band, allowance 0 for every band after the first — and add the monthly costs together.

The formula.

Step one normalises the volume to decimal gigabytes, because the price is per gigabyte and the two prefix systems are not interchangeable. The factors are exact rather than rounded: a gibibyte is 2³⁰ = 1,073,741,824 bytes and a gigabyte is 10⁹, so the ratio is exactly 1.073741824; a tebibyte is 2⁴⁰ bytes, exactly 1099.511627776 GB. The binary prefixes were standardised by the IEC in 1998 precisely to end this ambiguity, and NIST publishes the table; the industry has partially ignored it ever since, which is why the selector exists.

Step two subtracts the free allowance and floors the result at zero. A month entirely inside the allowance bills nothing, and the calculator reports a billable volume of zero rather than a negative one.

Step three multiplies billable volume by the rate. That is the bill. The annual figure multiplies it by twelve, which assumes a flat volume — if your traffic is growing, treat it as a floor rather than a forecast.

Step four computes two things the invoice does not show you. The allowance's value is the portion of the allowance you actually consumed, times the rate — if you moved 50 GB against a 100 GB allowance, it saved you 50 GB worth, not 100. The blended rate is the bill divided by the total volume including the free portion. It is always at or below the headline rate and converges on it as volume grows, which is the arithmetic behind the observation that free tiers are a rounding error at scale.

Step five converts the volume into an average sustained bit rate, purely as a cross-check. One decimal gigabyte is 10⁹ bytes, which is 8 × 10⁹ bits, which is 8,000 megabits. A day is 86,400 seconds. So the mean rate in Mbps is volume × 8000 ÷ (days × 86,400). This is a mean, not a peak, and links must be sized to peaks — a service whose traffic follows an ordinary daily curve will peak at several times its mean, and sizing a circuit to the mean guarantees congestion for the busiest hours of every day.

What the model deliberately does not do: graduated tier bands, committed-use or reserved discounts, private interconnect rates, inter-region and inter-zone transfer, per-request charges, and currency conversion. Each of those is provider-specific and changes often enough that encoding it would make the page wrong rather than useful. The flat band is the piece that is stable, and it is the piece implemented here.

A worked example.

Frequently asked questions.

References& sources.

1. [1]Amazon Web Services, Amazon EC2 On-Demand Pricing — 'Data Transfer' section. Source of the free-allowance structure quoted on this page: 'AWS customers receive 100 GB of free data transfer out to the internet free each month, aggregated across all AWS Services and Regions (except China and GovCloud)', together with the notes that rate tiers take aggregate cross-service usage into account and that customers above 500 TB/month should contact sales. Fetched 2026-07-28; no per-GB rate is attributed to AWS anywhere on this page, because none was present in the fetched content.
2. [2]Google Cloud, Free Tier usage limits documentation. Quoted as the contrast case for how far free allowances differ between providers: Compute Engine grants '1 GB of outbound data transfer from North America to all region destinations (excluding China and Australia) per month'. Fetched 2026-07-28.
3. [3]NIST, 'Prefixes for binary multiples' (Reference on Constants, Units and Uncertainty). Source of the IEC 1998 binary prefixes used by the unit selector — kibi 2¹⁰, mebi 2²⁰, gibi 2³⁰ = 1,073,741,824, tebi 2⁴⁰ — and of the decimal-versus-binary ambiguity that makes a GiB 7.4% larger than a GB.
4. [4]NIST Special Publication 330, section 4, Table 8 — non-SI units accepted for use with the SI. Source of the day constant used in the average sustained rate: 1 d = 24 h = 86 400 s.
5. [5]RFC 5136, 'Defining Network Capacity' (IETF, 2008). The definition the average sustained rate is measured against — IP-layer capacity as 'the maximum number of IP-layer bits that can be transmitted … divided by I' — and the warning that 'literature often overloads the term bandwidth to refer to what we have described as capacity in this document'.