TechWindo

MCS Table MCS Index (0..28) Layers (ν)

PRBs (N_PRB) Data symbols/slot (N_symb,sh) DM‑RS RE per PRB (N_DMRS,PRB) Overhead RE per PRB (N_oh,PRB)

TB scaling Small‑TBS method

N’RE = 12·N_symb,sh − N_DMRS,PRB − N_oh,PRB; N_RE/PRB = min(156, N’RE)

Notes (3GPP alignment)

MCS tables and Qm/R come from TS 38.214 §5.1.3.1 Tables 5.1.3.1‑1/‑2/‑3. [2](https://www.sharetechnote.com/html/5G/5G_MCS_TBS_CodeRate.html)
N’RE and 156‑RE cap per PRB follow the examples used in TS 38.214 sources (RE accounting within a PRB). [3](https://www.sqimway.com/nr_pdsch.php)
TBS uses the §5.1.3.2 two‑branch method with small‑block threshold 3824 bits. The default “Round‑to‑6‑bit” option mirrors common reference tools; request “spec‑table” if you need the exact discrete set. [4](https://www.rfwireless-world.com/calculators/5g-nr-tbs-calculation)[5](https://5g-tools.com/5g-nr-tbs-transport-block-size-calculator/)

Background (you can paste near the widget)

Qm/R selection: Choose the MCS table and index; Qm and target code rate R come from TS 38.214 §5.1.3.1 (Tables 1–3).
RE accounting: For an allocation of Nsymb,sh symbols, the usable RE/PRB is N’RE = 12·Nsymb,sh − NDMRS − Noh, capped to 156 RE/PRB.
TBS determination: Form Ninfo = NRE × R × Qm × ν × tbScaling, then apply the ≤ 3824 / > 3824 procedures in TS 38.214 §5.1.3.2. (This calculator uses the common 6‑bit quantization for small TBS; on request, I can switch to a spec‑exact discrete set.)

January 31, 2026