What size is Letter paper in pixels?
US Letter is 8.5 × 11 inches (215.9 × 279.4 mm). Multiply those dimensions by the intended PPI to get raster pixel dimensions.
Use the numbers from your actual job
The guide explains the decision; the linked calculator gives you the value for your own file or production assumptions.
Separate physical paper size from raster resolution
Paper dimensions are physical. Pixel dimensions only appear after a PPI is chosen, while scaling decisions depend on the A-series geometry or the exact source/target sheet dimensions.
Apply the answer to this specific question
US Letter is 8.5 × 11 inches (215.9 × 279.4 mm). Multiply those dimensions by the intended PPI to get raster pixel dimensions. The practical consequence should be checked with Letter Paper Pixel Calculator when your own dimensions, page count, cost or production values differ from the example implied by the question.
What commonly changes the result
For “What size is Letter paper in pixels?”, the most important variables are the ones represented by the linked calculator and any provider-controlled specification. A correct arithmetic result can still be unsuitable if the source dimensions, category, page yield, trim, bleed, margin or production method were assumed incorrectly.
A better verification workflow
For What size is Letter paper in pixels?, record the source measurement or controlling specification first, then run the real job values through letter pixels. Keep the result with the job notes, compare it with the physical file or material, and recheck any provider-controlled rule immediately before production or upload.
Practical answer
US Letter is 8.5 × 11 inches (215.9 × 279.4 mm). Multiply those dimensions by the intended PPI to get raster pixel dimensions.
When the decision affects a paid print run, book upload, client order or expensive material, keep the calculation with the job notes and verify any external specification again immediately before production.