Model Athena cost per TB scanned and see how partition pruning, column projection and Parquet compression cut the bill.
Athena charges only for bytes read from S3, and three independent multipliers reduce that: partition pruning skips whole prefixes before any file is opened, columnar formats read only the columns referenced, and compression shrinks what is left. They multiply, so 90% pruning with 20% of columns at 4x compression scans half a percent of the table — but SELECT * on CSV gets none of the three. The price per TB is an editable input with a realistic us-east-1 default, so confirm the current Athena rate with AWS for your region. Converting a raw CSV lake to partitioned Parquet routinely cuts Athena spend by 95% or more with no query changes, and this is the arithmetic that justifies the conversion job.
Athena Query Cost
scanned per query = table GB × (1 − pruning) × column share ÷ compression ratio, floored at the 10 MB minimum; cost = total TB scanned × price per TB.
scanned per query = table GB × (1 − pruning) × column share ÷ compression ratio, floored at the 10 MB minimum; cost = total TB scanned × price per TB. Athena charges only for bytes read from S3, and three independent multipliers reduce that: partition pruning skips whole prefixes before any file is opened, columnar formats read only the columns referenced, and compression shrinks what is left. They multiply, so 90% pruning with 20% of columns at 4x compression scans half a percent of the table — but SELECT * on CSV gets none of the three. The price per TB is an editable input with a realistic us-east-1 default, so confirm the current Athena rate with AWS for your region.
Converting a raw CSV lake to partitioned Parquet routinely cuts Athena spend by 95% or more with no query changes, and this is the arithmetic that justifies the conversion job.
This calculator takes 7 inputs: Table size if scanned in full, Data eliminated by partition filters, Share of columns the query reads, Compression ratio of the stored format, Queries per month, Athena price, Minimum billed scan per query. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.
It defeats column projection, so Athena reads every column of every surviving file. On a 200-column table where your query needs three columns, that is roughly 60x more bytes scanned — and bytes scanned is the whole bill.
Cancelled queries are billed for the data scanned up to the point of cancellation, and queries that fail with an error are not billed. Every successful query is billed for at least 10 MB even if it touches less.