What's the difference between TPM vs FPKM?

TPM (Transcripts Per Million) and FPKM (Fragments Per Kilobase of transcript per Million mapped reads) are both RNA-seq normalization methods. FPKM adjusts for sequencing depth and gene length but can’t be directly compared across samples. TPM improves comparability by scaling gene expression so that transcript proportions sum consistently across samples, making it more widely used.