CMU Rebar Calculator: Count, Spacing & Cut List
Plan vertical and horizontal reinforcing for CMU walls. Enter wall size, spacing, stock length, splices (e.g., 40 db minimum), and end development allowances. Get rebar counts, total lengths, estimated weight, and a simple cut list grouped by piece length. Notes, formulas, and sources included.
Results
Vertical bars
Count (incl. ends & jambs): 0
Bars per line: 0
Per-bar required length (incl. dev): —
Segments per bar: 0 • Splices per bar: 0
Total steel length: — • Approx. weight: —
Horizontal bars (bond beams)
Layers: 0
Per-layer required length (incl. ends): —
Segments per layer: 0 • Splices/layer: 0
Total steel length: — • Approx. weight: —
Grand totals
Total length: —
Estimated weight: —
Cut List (grouped lengths)
| Type | Bar size | Qty | Length | Note |
|---|
Cut list assumes repeating stock-length segments; last segment on each bar/run is the “remainder”. Laps are included as overlaps (extra steel).
How to use this rebar calculator
- Select metric or US units.
- Enter wall length/height and course (module) height.
- Choose vertical spacing (or custom), end bars, and optional jamb pairs for openings.
- Choose bond-beam frequency and whether to include the top course.
- Set stock length, splice (e.g., 40 db min 300 mm / 12 in), and simple end development allowances.
- Pick bar sizes for vertical and horizontal. Review counts, total length, weight, and the grouped cut list.
Formulas & assumptions
- Vertical bar positions:
n = ⌈L / s⌉ + endBars, where s is vertical spacing; add2 × openingsfor jamb pairs. - Vertical per-bar length:
Lv,req = H + devbase + devtop. - Splice length:
Llap = max(lapDb × db, lapMin)(editable defaults shown). - Segments per vertical:
k = ⌈ Lv,req / (Lstock − Llap) ⌉ifLstock > Llap, else large number (increase stock length or reduce lap per code). - Total vertical steel:
Lv,tot = n × ( Lv,req + (k−1)×Llap ). - Bond-beam layers: courses =
⌈H / courseH⌉; layers every N courses plus optional top course. - Per-layer length:
Lh,req = L + 2×devend(we usedevtopfor ends); segments per layer by same splice logic. - Total horizontal steel:
Lh,tot = layers × ( Lh,req + (k−1)×Llap ). - Weights: US bars use standard lb/ft table; metric bars use
kg/m ≈ dmm² / 162. Totals shown in both units. - Scope: Planning estimate. Actual splice/development per current TMS 402/602 design, project specs, bar grade, grout strength, and confinement. Follow your engineer’s details.
References
- Standard CMU modular coursing (≈8 in / 203 mm module). :contentReference[oaicite:0]{index=0}
- US bar size weights (lb/ft) (#3–#8). :contentReference[oaicite:1]{index=1}
- Masonry lap splices & development (overview/NCMA TEK 12-06A; lap = development length per TMS 402). :contentReference[oaicite:2]{index=2}
- Typical stock lengths (20 ft, 40 ft). :contentReference[oaicite:3]{index=3}
- Metric CMU course metrics (200 mm nominal). :contentReference[oaicite:4]{index=4}
FAQs
Why does the total steel include extra length for splices?
Lap splices overlap bars, so each splice adds steel equal to the lap length. The calculator adds this to total length (and weight) for ordering realism.
Is 40 db always correct for lap length?
No. TMS 402 sets lap equal to development length, which depends on bar size, grout strength, location, and confinement. Use the editable fields to match your engineer’s details. :contentReference[oaicite:5]{index=5}
How accurate is the cut list?
It assumes most segments are stock-length with a single “remainder” piece on each bar/run. Fabricators may optimize differently; share this as a starting schedule.