MENDNOOK / RESEARCH & METHODS
How MendNook calculators work
Published input definitions, formulas, units, examples and stop conditions. These are planning tools, not automatic order specifications.
Method version: 1.0. Source review: 2026-11-04. Data class: deterministic geometry and illustrative input values; no field measurements.
1. Screen material and spline
Inputs: outside frame width W, height H, user-selected mesh cut allowance A per side, and spline shopping allowance p percent. All lengths must use the same units.
Equations: cut width = W + 2A; cut height = H + 2A; cut area in square feet = (cut width × cut height) / 144 when all measurements are inches; frame perimeter = 2(W + H); spline shopping length = perimeter × (1 + p/100).
Worked example: W = 30 in, H = 24 in, A = 1 in on each side, p = 10%. Mesh cut = 32 × 26 in, mesh cut area = 5.78 sq ft; frame perimeter = 108 in (9 ft); shopping spline length = 118.8 in (9.9 ft).
Limit: the outside-frame approach is a MendNook planning convention, not a universal Phifer cut dimension. Phifer describes measuring relative to spline-channel edges for some installations; never substitute the example allowance for the instructions of the exact screen frame or material. Spline length cannot determine spline diameter. Mesh may have weave orientation and roll-width constraints.
Source: Phifer screen installation and material guidance. Use the single-screen tool or multi-screen planner.
2. Inside-mount blind measurement worksheet
Inputs: three opening widths (top, middle, bottom) and three opening heights (left, center, right), taken consistently at the intended installation plane.
Equations: Wmin = minimum of the three widths; Hmax = maximum of the three heights; Hmin = minimum of the three heights. All are observed opening dimensions, not order dimensions until you identify the exact product instructions.
Worked example: widths 35.5, 35.375 and 35.25 in; heights 60.125, 60.375 and 60.25 in. Wmin = 35.25 in, Hmax = 60.375 in, Hmin = 60.125 in. Which height to submit depends on product type.
Limit: Blinds.com describes different instructions for inside-mount wood blinds, vertical blinds and Quick Ship products. The tool cannot infer mounting-depth sufficiency, fabric deductions or a brand-specific SKU rule. See our three-source comparison.
Sources: Blinds.com wood blind measuring guide; vertical blinds; Quick Ship blinds. Use the worksheet helper.
3. Three-point exterior door clearance
Inputs: closed-door hinge-side gap g1, center gap g2 and latch-side gap g3 measured to the same threshold surface. Record door swing and conditions separately.
Equations: minimum clearance = min(g1,g2,g3); maximum clearance = max(g1,g2,g3); observed variation = max − min.
Worked example: 3/16, 1/4 and 5/16 in give min 3/16 in, max 5/16 in and variation 1/8 in. An average alone hides possible sweep drag at the smallest gap and inadequate seal contact at the largest.
Limit: three samples may miss local high spots, threshold movement or door alignment. No generic pass/fail tolerance is inferred. DOE advises checking door adjustments before weatherstripping.
Source: U.S. DOE exterior-door weatherstripping job aid. Use the door gap checker.
4. Weatherstrip run length
Inputs: top run T, hinge jamb L, latch jamb R and extra shopping percentage p. Units must match.
Equations: base length = T + L + R; shopping length = base × (1 + p/100).
Worked example: 36 + 80 + 80 = 196 in. With 10% allowance, 215.6 in = 17.97 ft. The calculator checks continuous, unspliced cuts separately when roll length is entered; total feet alone cannot establish the number of rolls.
Limit: this excludes the door bottom sweep and does not select gasket profile, kerf dimensions, compression, adhesive, fire rating or compatible stock. Actual corner treatment may change cut lengths. Follow the chosen manufacturer instructions.
Source: U.S. DOE exterior-door job aid. Use the length calculator.
5. Rectangle-frame diagonal
Inputs: outer rectangle width W and height H in the same units, plus optional measured corner-to-corner diagonals d1 and d2.
Equations: theoretical diagonal = square root of (W squared + H squared), by the Pythagorean theorem; measured diagonal difference = absolute value of (d1 − d2).
Worked example: W = 30 in and H = 24 in give a theoretical diagonal of 38.42 in. Different real diagonal readings may indicate a skewed frame, inconsistent reference points or measurement error.
Limit: equal diagonals do not prove that a frame is rigid, flat, undamaged or suitable to order. There is no universal manufacturer fit tolerance in this calculator.
6. Window-screen ordering reference: source comparison
Question: Does a generic “subtract 1/8 inch” instruction always produce a valid replacement screen size? No. Published screen supplier instructions describe different reference edges and retention systems. An unlabeled opening measurement is insufficient to establish a finished-screen order size.
Scope: original desk comparison of existing documents only, source checked 2026-11-02; zero on-site measurements, zero manufactured screens tested. This section is not a lab study, failure rate or approved fit tolerance.
The current Metro Screenworks reference describes a retaining-lip procedure with an example of adding 1/8 in vertically relative to its named reference. Its older measurement blog describes subtracting 1/8 in vertically. The spring-screen handout has its own channel/spring-specific conditions and describes an optional allowance. These passages cannot be used interchangeably without identifying the endpoints and mounting arrangement.
| Document scenario | Hypothetical reference | Example arithmetic | Result | Limitation |
|---|---|---|---|---|
| Current retaining-lip example | 30 in | 30 + 1/8 | 30 1/8 in | Only with its specific vertical reference |
| Older blog example | 30 in | 30 − 1/8 | 29 7/8 in | Document-specific measurement endpoints |
| Spring-screen handout | 30 in | Conditional | Not determined | Requires exact spring, deepest channel and supplier confirmation |
Controlled numerical difference: 30 1/8 − 29 7/8 = 1/4 inch. This compares illustrative arithmetic using one intentionally fictional reported value, not dimensions measured on the same actual screen. Neither number is safe to use as an order size without product-specific confirmation.
Reproduce: read each linked original manual and label its starting measurement surface; enter the hypothetical 30-in reading only for that document; apply its sign condition; subtract the two illustrative outcomes. Download inputs, outcomes and source URLs (CSV). If references differ or hardware is unknown, mark order size pending supplier guidance.
Practical next step: take a photograph of the bottom lip, deepest upper channel and spring/clip positions next to a ruler, then request confirmation from the screen supplier. Also see the replacement-screen measurement guide and our measurement-path assistant.
Conversions and rounding
Exactly 1 international inch = 25.4 mm; exactly 1 ft = 12 inches. Convert before applying a formula and retain enough digits internally; display rounding must not be treated as an order measurement. Do not infer a supplier rounding rule from this page.
Corrections, evidence and reuse
These formulas are arithmetic applied to example inputs. Where a manufacturer specifies a different measurement plane, allowance, rounding or height convention, that source controls the product order. The worked examples were not tested on installed products. Contact our corrections desk with the exact source and model if you identify a discrepancy.