CMU wall rebar calculator

1. Vertical bars at the spacing
   wall length ÷ spacing, rounded up, + 1 (a bar at each end)
   40 × 12 ÷ 48 (in), rounded up, + 1 = 11
2. Lap length
   bar diameter × lap diameters
   #5: 0.625 × 48 (in) = 2' 6"
3. Vertical steel
   bars × wall height
   11 × (10) (ft) = 110' 0"
4. Bond-beam steel
   bond beams × bars each × (length + laps)
   1 × 2 × (40 + 2 × 2.5) (ft) = 90' 0"
5. #5 weight
   feet × lb per foot (ASTM A615)
   200 × 1.043 = 208.6 lb
6. #5 stock bars
   full pieces + cut pieces packed into stock bars
   20' bars = 10

Where the numbers come from

• Bar layout: Vertical: ⌈wall length ÷ spacing⌉ + 1 (a bar at each end) + 2 per opening; bond beams: bars × wall lengthGeometry only. Real bars sit in the block cells, so the spacing is a multiple of 8" and a bar can move a cell to clear an opening or a control joint. Bars at corners, wall intersections and jambs follow your structural drawings.
• Lift bars (6'8"): Low-lift grouting: build at most 5'4", set the bars, grout, repeat — bars are spliced at each pour heightCMHA CMU-FAQ-005: low-lift sections are no taller than 5'4" and "continuity of the reinforcement is maintained by splicing between each section". 6'8" (80") is a 20' bar cut in three with no waste, short enough for the mason to lift block over. In a 4' (48") lift it sticks up 80 − 48 = 32" — a full lap for #4 (24") and #5 (30") at 48 diameters, but not #6 (36"). A new bar is set at every pour height, so pieces per location = ⌈(height − bar) ÷ lift⌉ + 1, each lapping the one below by bar − lift, with the top piece cut to fit.Source
• Lap length: 48 bar diameters for Grade 60 (#4 = 24", #5 = 30", #6 = 36")The IBC 2107.2 alternative for allowable stress design, as summarized by ENERCALC: 40 diameters for 40 ksi bars, 48 for 60 ksi. The TMS 402 development-length equation (Eq. 6-1) depends on masonry strength, cover and bar size and often gives longer laps (up to 72 diameters) — use the lap on your structural drawings when it is given.Source
• TMS 402 lap equation: ld = 0.13 × db² × fy × γ ÷ (K × √f′m), at least 12"; γ = 1.0 (#3–#5), 1.3 (#6–#7), 1.5 (#8+)Masonry Advisory Council summary of TMS 402. K is the smallest of the cover, the clear spacing between splices and 9 db. Not computed here — it needs f′m and cover from the design.Source
• Drill-in dowels: One per vertical bar; length = embedment (4" default) + one lap above the slab or footingThe first vertical bar laps the dowel. The embedment is your engineer's or the adhesive report's number — 4" is only the default; adhesive makers list minimum embedments per bar size (e.g. Hilti HIT-HY 200 V3: #4 2¾", #5 3⅛", #6 3½").
• Epoxy per anchor: Average of the gap (π ÷ 4 × (hole² − steel²) × embedment) and the hole ⅔ full (⅔ × π ÷ 4 × hole² × embedment)Installers fill the hole about ⅔ full; what the anchor pushes out of the hole is lost, so the real use is between the gap alone and the ⅔ fill — taken as the average of the two. The total is rounded up to a whole fl oz. Waste, if entered, is added on top for rough holes and hard conditions.
• Drilled hole size (ANSI B212.15): Carbide bit tips (in.): 7/16 0.458–0.468 · ½ 0.520–0.530 · 9/16 0.582–0.592 · ⅝ 0.650–0.660 · 11/16 0.713–0.723 · ¾ 0.775–0.787 · ⅞ 0.905–0.917 · 1 1.030–1.042 · 1⅛ 1.160–1.175 · 1⅜ 1.410–1.425 · 1½ 1.535–1.550A bit drills a little over its name; the hole is taken at the middle of the range (7/16 → 0.463, ⅞ → 0.911, 1½ → 1.5425). A hole size you type that is not a standard bit is used as typed.Source
• Threaded rod steel: d − 5√3 ÷ 16 × pitch: halfway between the outside of the rod and its thread root (d − 5√3 ÷ 8 × pitch) · UNC ⅜-16, ½-13, ⅝-11, ¾-10, ⅞-9, 1-8, 1¼-7Thread geometry (ASME B1.1, H = √3 ÷ 2 × pitch). The epoxy fills the thread grooves, so a rod holds less steel than a solid bar of its size (¾" → 0.6959", ½" → 0.4584"). Rebar uses its nominal size (#10 = 1.270").
• Extension tube: Past 8" deep: (embedment − 8") × 0.17 fl oz per inch, a new tube every 10 anchorsA mixing nozzle reaches about 8"; deeper holes are filled from the bottom through an extension tube, which holds 0.17 fl oz per inch (the inside of a ⅝" bore: π ÷ 4 × 0.625² = 0.307 in³ per inch) and is replaced every 10 anchors.
• Cartridges: Sizes in mL as printed, fl oz worked out (mL ÷ 29.5735) · Hilti HIT-HY 200 V3 330 / 500 mL = 11.2 / 16.9 fl oz · DeWalt AC100+ Gold 280 / 825 mL = 9.5 / 27.9 fl ozWhat a cartridge really gives, after the nozzle and the first mix: 9.07 fl oz from the 9.5 oz and 27.29 fl oz from the 28 oz AC100+ Gold. Hilti lists none, so its packs are taken at 96%.
• Hilti HIT-HY 200 V3: Bits: rod ⅜→7/16 · ½→9/16 · ⅝→¾ · ¾→⅞ · ⅞→1 · 1→1⅛ · 1¼→1⅜ · rebar #3→½ · #4→⅝ · #5→¾ · #6→⅞ · #7→1 · #8→1⅛ · #10→1½ · foil packs 330 and 500 mLHilti Anchor Fastening Technical Guide Ed. 22, Table 38 (threaded rod) and Table 18 (rebar); the same bits in grouted CMU (Masonry Anchor Design Guide 2023, Table 1); ICC-ES ESR-4868 (revised April 2026) §3.2.1 for the 330 / 500 mL packs. Hilti lists a bigger bit for deep embedment (#6 1", #7 1⅛", #8 1¼") — type it if you drill that deep. Hilti's own Volume Calculator is a phone app.Source
• DeWalt AC100+ Gold: Bits: rod ⅜→7/16 · ½→9/16 · ⅝→11/16 · ¾→⅞ · ⅞→1 · 1→1⅛ · 1¼→1⅜ · rebar #3→7/16 · #4→⅝ · #5→¾ · #6→⅞ · #7→1 · #8→1⅛ · #10→1½ · cartridges 280 mL (8478SD-PWR) and 825 mL (8490SD-PWR)DeWalt AC100+ Gold Technical Guide ©2025 rev. K (p. 2 installation, p. 29 ordering), matching ICC-ES ESR-2582 (Feb 2026) Table 9. Approved for rebar used as an anchor (embedment up to about 12 bar diameters), not for post-installed rebar development or splices.Source
• Hole size rule (the cross-check): Bit = anchor + adhesive ring, in 1/16" steps: rod + 1/16" up to ⅝", + ⅛" above · rebar (actual size) + ⅛" · every maker's bit is checked to leave 1/32"–3/16" of ring each sideA cross-check on every maker's bit, and the answer wherever a maker's number cannot be found. Makers may call for a different size — type your hole size if so.
• Method source: DeWalt Adhesive Anchor Volume EstimatorThe ⅔ fill, the extension tube and the usable cartridge follow it; every number on this page is also worked out by math.Source
• Rebar weights (ASTM A615): #4 0.668 · #5 1.043 · #6 1.502 · #7 2.044 · #8 2.670 lb/ftThe same table the rebar calculator uses: bar area × 3.40 lb/ft per in².Source
• Stock bars: Lapped bars use full stock pieces plus a cut piece; lift bars and cut pieces are packed into stock bars longest firstOffcuts that fit another cut piece are reused — three 6'8" lift bars come out of one 20' bar. Waste, if entered, is added to the stock bar count only.