Concrete curb calculator

1. Section area
   A = W × H
   8" × 8" = 64.00 in²
2. Concrete
   V = A × length
   0.4444 SF × 20' 0" = 0.33 CY
3. Weight
   W = V × 140 lb/ft³
   8.89 ft³ × 140 lb/ft³ = 1,245 lb
4. Contraction joints
   n = ⌈length ÷ 10 ft⌉ − 1 (10 ft apart at most)
   ⌈ 20' 0" ÷ 10' 0" ⌉ − 1 = 1
5. Dowels
   n = ⌈length ÷ spacing⌉ + 1
   ⌈ 20' 0" ÷ 1' 0" ⌉ + 1 = 21
6. Each U-shaped dowel
   ℓ = 2 × (drilled depth + curb height − cover) + (width − 2 × cover)
   2 × ( 4" + 6" ) + 4" = 2' 0"
7. Dowels, total length
   Σ = n × ℓ
   21 × 2' 0" = 42' 0"
8. Holes to drill
   two legs per U-shaped dowel
   21 × 2 = 42
9. Drilled hole (in)
   a carbide bit drills the middle of its ANSI B212.15 range
   5/8" bit: ( 0.650 + 0.660 ) ÷ 2 = 0.6550
10. Hole volume
    π ÷ 4 × drilled hole² × embedment
    π ÷ 4 × 5/8" ² × 4" = 1.35 in³
11. Just the gap
    hole − steel (π ÷ 4 × steel² × embedment)
    1.35 in³ − 0.79 in³ = 0.56 in³
12. Hole ⅔ full
    ⅔ × hole (the instructions say fill the hole about ⅔ full)
    ⅔ × 1.35 in³ = 0.90 in³
13. Epoxy per anchor
    (gap + ⅔ fill) ÷ 2
    ( 0.56 in³ + 0.90 in³ ) ÷ 2 = 0.73 in³
14. All anchors
    per anchor × anchors (+ tube), rounded up to a whole fl oz
    0.73 in³ × 42 = 18 fl oz
15. One cartridge gives
    cartridge less the nozzle and first-mix loss
    27.9 fl oz = 27.29 fl oz
16. Cartridges
    all anchors ÷ one cartridge, rounded up
    18 fl oz ÷ 27.29 fl oz = 1
17. Each longitudinal bar
    ℓ = length − 2 × cover
    20' 0" − 2 × 2" = 19' 8"
18. Longitudinal bars, total length
    Σ = bars × ℓ
    4 × 19' 8" = 78' 8"
19. #4 weight
    W = Σ × 0.668 lb/ft
    120' 8" × 0.668 lb/ft = 81 lb
20. #4 stock bars to buy
    full stock bars + bars the cut pieces are packed into (longest first, offcuts reused)
    0 full + 7 for cut pieces = 7

Where the numbers come from

• Sidewalk curb (NYC DOT H-1044): Concrete curb: 6" top, 8" bottom, 18" deep (minimum), 7" reveal, top slopes ¼" toward the street · Curb on a slab: 8" × 8" or 4" × 8" (or your sizes), every side exposedNYC DOT Standard Details of Construction, H-1044 "Concrete Curb" (issued 7/1/10, PDF page 38). The depth depends on the pavement design: 18" to 27" (Standard Highway Specifications §4.08). The back is vertical, so the 2" lean is on the street face, over the full depth. The area is worked from the corners of the shape (straight lines); the 1" rounded top edge is not taken off, so the concrete is a little more than the exact shape, never less. The curb on a slab is not a standard shape. Use your drawings when they differ.Source
• Curb on a slab (typical structural detail): #4 dowels @ 12": an upside-down U with both legs drilled into the slab (one straight bar for curbs 5" wide or less) · #4 on each face at levels ≤ 12" apart · 2" cover · height ≤ 3 × widthA typical structural detail for concrete curbs on slabs, as structural engineers draw it on commercial jobs (not a public standard, so no link). The detail asks for the dowels to go 12" into the slab, or what the epoxy maker needs to fully develop the bar; the page starts at 4" drilled — use your drawings. For curbs 12" or wider the detail puts a #5 on top. The U-shaped dowel is measured out to out (no bend deduction).
• Joints: Built in 10 ft sections with ¼" joints, lined up with the sidewalk jointsNYC DOT Standard Highway Specifications §4.08 "Curb, Concrete" (5/16/2022): 10 ft independent sections, ¼" joints filled with preformed material. Shown for information — joints are not a material.Source
• Curb reinforcing (TxDOT CCCG-21): Bars No. 4 · dowel bars and transverse bars at 4 ft c-c · 2 longitudinal bars in a curbTxDOT standard "Concrete Curb and Curb and Gutter" CCCG-21 (Feb 2021), notes 3, 6 and 8. NYC DOT's standard curb (H-1044) is plain concrete; its reinforced curb (H-1035) has 4 #4 bars and #2 ties at 18" with 2" cover. Sidewalk curbs go on the ground with no dowels; a curb on a slab is dowelled down into it, drilled 6" (half of TxDOT's 12" Bar C) and set in epoxy. Dowels are counted ⌈length ÷ spacing⌉ + 1 (one at each end). U-bars are measured out to out with no bend deduction (a little more steel, never less). Use your drawings when they show the steel.Source
• Cover: 1½" for #5 and smaller exposed to weatherACI 318-19 Table 20.5.1.3.1: 1½" (#5 and smaller) or 2" (#6 and larger) for concrete exposed to earth or weather; 3" cast against the ground. Bars are cut the cover short at each end.Source
• Tie hooks (135°): Length one 135° tie hook adds: #3 4¼", #4 4¾", #5 6" (CRSI) · #2 3.89" (worked out)CRSI Manual of Standard Practice, 29th ed., Table 7-2 as revised (errata, uncoated bars). Other sizes by the bend math: the 135° arc on the bar's centre line + the straight extension (ACI 318 Table 25.3.2: 6 bar diameters, at least 3") − (half the bend + one bar). With CRSI's own bends (#4 2½", #5 3¼", about 5 bar diameters) this gives CRSI's #4 and #5, so #2 (¼" plain, in neither table — ACI wants ties #3 or larger) is worked out with a 5-diameter bend: 3.89"; #6–#8 with ACI's 6 diameters. A U or tie narrower than the tightest ACI bend (4 bar diameters inside for #3–#5) is flagged. NYC DOT H-1035 reinforced curb: 4 #4 bars and #2 ties at 18", 2" cover all round. Ties are measured out to out with no bend deduction (a little more steel, never less).Source
• Lap splice (ACI 318-19 Class B): 4,000 psi, Grade 60, uncoated: #3 19" · #4 25" · #5 31" · #6 37" · #7 54" · #8 62" · #9 70" · #10 79" · #11 87"Class B tension lap = 1.3 × ℓd (§25.5.2.1), ℓd from Table 25.4.2.3: fy ÷ (25 λ √f'c) × db for #6 and smaller, ÷ 20 for #7 and larger, rounded up, at least 12". Assumes bars not cast with more than 12" of concrete below them, uncoated, cover ≥ db and spacing ≥ 3 db — usual for a slab grid. Lightweight concrete: λ = 0.75 (longer lap). Same as Table 1.11 of the Dayton Superior Rebar Splicing Handbook (Other bars, Case 1, Class B) at 3,000 and 4,000 psi; at 5,000 psi #4, #6, #8 and #10 come out 1" longer here because they are rounded up. Use the lap on your structural drawings when it is given.Source
• Rebar weights (ASTM A615): #3 0.376 · #4 0.668 · #5 1.043 · #6 1.502 · #7 2.044 · #8 2.670 · #9 3.400 · #10 4.303 · #11 5.313 lb/ftASTM A615 Table 1 nominal weights, as listed on Harris Supply Solutions' "Concrete Reinforcing Bar Products" sheet. Each equals the bar area × 3.40 lb/ft per in² (steel at about 490 lb/ft³): #4 = π × 0.5² ÷ 4 = 0.1963 in² × 3.40 = 0.668 lb/ft.Source
• Weight of normal-weight concrete: 140 lb/ft³QUIKRETE 5000 data sheet, Table 1: unit weight (ASTM C138) approximately 140 lb/ft³. Ready-mix is often 145–150 lb/ft³ — check your mix ticket.Source
• Cubic yard: 1 CY = 27 ft³ = 0.764555 m³Exact by definition: 1 ft = 0.3048 m.
• 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