Formula used
The calculator totals all joint runs where sealant is applied: Perimeter, Internal joints, Opening perimeters, and Extras.
- Perimeter joints: P = 2(L + W) (when enabled).
- Internal joints by spacing: for spacing s, segments = ceil(D / s), joints = segments − 1, length = joints × cross-dimension.
- Openings: Length = count × opening perimeter.
- Waste: Final = Total × (1 + waste% / 100).
- Sealant quantity (optional): Volume = Final length × width × depth. The estimate converts to mL and divides by cartridge size.
Practical note: Joint design, backer rod, and substrate movement can affect quantity.
How to use this calculator
- Select Units and your preferred Method.
- For rectangular surfaces, enter length, width, and joint spacing.
- Add openings and any extra linear joints for transitions.
- Set a realistic waste percentage for site conditions.
- Enable quantity estimate if you know width and depth.
- Press Calculate, then download CSV or PDF if needed.
Example data table
| Case | Surface (L × W) | Spacing (L / W) | Openings | Extra | Waste | Total length |
|---|---|---|---|---|---|---|
| Small slab | 12 m × 8 m | 4 m / 4 m | 2 @ 3.6 m | 5 m | 5% | ≈ 101.7 m |
| Facade bay | 30 m × 10 m | 6 m / 5 m | 6 @ 5.0 m | 10 m | 7% | ≈ 233.0 m |
| Custom segments | — | — | — | Sum 18.5 m | 3% | ≈ 19.1 m |
Values are illustrative; your joints and openings will vary.
Project inputs that drive joint length
Joint length follows geometry and detailing. For a rectangular bay, perimeter equals 2×(L+W). Internal joints depend on panel layout, so spacing along length and width controls how many joint lines form. Note units, rounding, and whether dimensions are net or gross, because returns, kerbs, or rebates change measured runs. Consistent clean inputs reduce rework and produce auditable takeoffs.
Surface-grid joints from spacing
Using spacing, internal joint lines are estimated as floor(L/spacingL)−1 and floor(W/spacingW)−1, then each line is multiplied by the opposite dimension. This matches common saw-cut and movement-joint grids. Example: 12 m × 8 m with 4 m spacing gives 2 lines one way and 1 the other, adding 2×8 + 1×12 = 28 m, plus perimeter. If spacing is blank, treat it as “no grid.”
Openings and transitions
Openings add joint runs around frames and penetrations. Enter the number of openings and an average perimeter per opening when sizes repeat. Add extra linear joints for transitions at material changes, control joints at corners, or slab-to-wall interfaces. For irregular shapes, switch to custom segments and sum lengths from CAD, then keep openings and extras as separate allowances for transparency.
Waste, sequencing, and reporting
A waste percentage captures overlaps, tool losses, and minor scope changes. Allowances vary by access and complexity; 5–10% is typical, while dense corner work may need more. Output separates base length from total with waste, helping distinguish design from procurement. CSV supports cost codes, and the PDF snapshot aids approvals, RFIs, and records.
Quantity estimate and procurement checks
Quantity estimation converts length into volume using bead width and depth: volume = length×width×depth. The calculator reports mL and cartridges using your selected cartridge size, enabling quick procurement checks. Verify backer rod, joint movement, and manufacturer limits, because bead geometry can change on site. Use the estimate for planning, then reconcile final orders with approved details and test areas.
FAQs
1) When should I use Rectangular surface versus Custom segments?
Use Rectangular surface for slabs or bays with a clear length and width. Use Custom segments when layouts are irregular, when joints are not on a uniform grid, or when lengths come directly from drawings or field measurement.
2) What does joint spacing represent in the calculator?
Spacing represents the planned distance between parallel joint lines. It estimates how many internal joint runs occur across the surface. Enter spacing from approved details; if there is no internal grid, leave spacing blank or set it to zero.
3) How do I account for doors, windows, or penetrations?
Add openings by quantity and an average perimeter per opening. This works well when sizes repeat. For mixed sizes, use a conservative average or calculate multiple groups, then combine results using extra linear joints.
4) What waste percentage should I apply?
Choose waste based on site complexity and access. Straight runs with good planning may use 5%. Congested corners, frequent stops, or vertical work may require 8–12%. Use prior project records where available and document your assumption.
5) How is sealant quantity and cartridge count estimated?
Quantity uses bead volume: length × width × depth, converted into milliliters. Cartridge count divides total milliliters by the selected cartridge size and rounds up. Treat this as a planning estimate; confirm bead geometry and manufacturer limits.
6) What do the CSV and PDF downloads include?
The downloads capture your latest calculation inputs and results, including method, totals, waste, and optional quantity data. CSV is convenient for spreadsheets and cost codes, while PDF provides a clean snapshot for submittals and records.