Craft Quantities
Plan & Takeoffs

Materials & Quantities

Blast-Resistant Fenestration Rating Checker

Check whether a glazing's published blast hazard rating meets a project's required protection level.

  • Answers as you type
  • Every formula cited
  • Calculated in your browser
SettingsSettings for this calculationUS
Market
Imperial · sales tax
The GSA performance condition already established for this glazing assembly by independent ASTM F1642 testing.

Find this value on the manufacturer's published test report or GSA-approved product listing — this tool does not derive it from geometry or pressure loads.

The minimum GSA performance condition the project's blast design criteria call for.

This comes from the project's threat/hazard assessment, typically set by a blast consultant or the governing security design criteria.

Achieved GSA performance condition

2 GSA Condition

ComparisonA comparison, not a check — no result here is an approval.

The glazing's published performance condition is at or above the project's requirement on the GSA/ASTM F1642 scale. Being on the right side of that comparison is not a blast design: this compares two published, independently-tested ratings and computes no blast pressure, impulse load or dynamic rebound response of its own. That work is done in SDOF or finite-element software per UFC 3-340-02 and ASTM F2248, by a qualified blast engineer.

Required condition
3 GSA Condition
Then change the inputs to see how far the answer moves.

Show calculation logic

How this was calculated

Formula source(s)

  • Full blast-resistant glazing design (dynamic rebound, pressure-impulse response) requires specialized SDOF/finite-element software (WINGARD, HazL) per UFC 3-340-02/ASTM F2248 — it cannot be reduced to a simple formula. This tool instead compares a glazing's already-published ASTM F1642/GSA hazard rating against the project's required performance condition, both on the standard GSA scale where a LOWER number is better (1 = best/no hazard, 5 = worst)

Inputs used

Glazing's Published GSA Performance Condition (1=best, 5=worst)
2
Project's Required GSA Performance Condition
3

Intermediate steps

Required condition
3 GSA Condition
Final result2 GSA Condition

Confidence note: The glazing's published performance condition is at or above the project's requirement on the GSA/ASTM F1642 scale. Being on the right side of that comparison is not a blast design: this compares two published, independently-tested ratings and computes no blast pressure, impulse load or dynamic rebound response of its own. That work is done in SDOF or finite-element software per UFC 3-340-02 and ASTM F2248, by a qualified blast engineer.

What this calculation does not cover

  • A performance condition is inseparable from the blast it was earned against. ASTM F1642 ratings come out of a shock tube or an arena test at a stated peak pressure and impulse, standing in for a particular charge at a particular standoff, so the same glass at half that standoff is a different result. Matching condition numbers without matching the pressure and impulse behind them is not a comparison.
  • The rating belongs to the tested assembly, not to the glass. The frame, the bite into it, the structural silicone or gasket, and the anchors back into the structure were all part of the specimen — swap any of them and the certificate no longer applies. Laminated glass that holds together in a frame that tears out of the wall puts the whole panel into the room.
  • The scale is written in terms of where fragments land, measured against a witness panel a set distance behind the opening. That makes one condition mean different things in different rooms: the rating that is comfortable across a deep lobby is a different proposition in a narrow corridor, or anywhere a desk sits hard against the glass line.

Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.0.1

Regulatory standards & verification citations1
  1. Full blast-resistant glazing design (dynamic rebound, pressure-impulse response) requires specialized SDOF/finite-element software (WINGARD, HazL) per UFC 3-340-02/ASTM F2248 — it cannot be reduced to a simple formula. This tool instead compares a glazing's already-published ASTM F1642/GSA hazard rating against the project's required performance condition, both on the standard GSA scale where a LOWER number is better (1 = best/no hazard, 5 = worst)

Which documents these citations point at

Standards referenced: ASTM F2248, ASTM F1642 (ASTM International, United States).

Cite this page

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Now that you have the number

These guides cover the work this quantity is for — the first ones run this calculator inside the section that raises the question.

Called something else where you work? Insulating glazing unit — the term in each market, how close the equivalence really is, and the standard that governs it.

How to calculate blast-resistant fenestration rating checker in 3 steps

  1. Glazing's Published GSA Performance Condition (1=best, 5=worst)The GSA performance condition already established for this glazing assembly by independent ASTM F1642 testing.
  2. Project's Required GSA Performance ConditionThe minimum GSA performance condition the project's blast design criteria call for.
  3. Achieved GSA performance conditionThe tool computes the achieved GSA performance condition from those figures and shows the formula, its sources, and a confidence rating alongside it.

Frequently asked questions

Does this tool calculate blast pressures or predict how the glass will actually respond to an explosion?
No. This tool only compares two already-established numbers — a glazing's published ASTM F1642/GSA hazard rating and the project's required performance condition. It does not model blast pressure, impulse, dynamic rebound, or fragmentation, all of which require specialized SDOF or finite-element software (e.g. WINGARD, HazL) per UFC 3-340-02/ASTM F2248, run by a qualified blast engineer.
Where do I find a glazing product's GSA performance condition?
It comes from independent ASTM F1642 test reports commissioned by the manufacturer, usually published on the product's technical data sheet or a GSA-approved product listing. Do not estimate or assume this value.
Why does a lower GSA condition number mean better performance?
The GSA scale is inverted from what you might expect: Performance Condition 1 represents no hazard (best), while Condition 5 represents the highest hazard (worst). A glazing meets the requirement when its achieved condition number is equal to or lower than the project's required condition number.
Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.