Built from real ductwork installation

Practical ventilation tools for work on site.

Fast calculators for duct fitters, installers and supervisors, with the working, source status and practical site guidance available when you need to check the result.

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Built by a duct fitterMade for mobileWorking and limits shown

VentTools calculators

Choose a site tool

The calculator opens first. Practical guidance and worked examples sit underneath.

Circular spiral ductwork forming a rolled offset on site

Ductwork Offset Calculator

Straight cut length, travel, roll angle and minimum rise using practical bend take-offs.

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Site-made rectangular-to-round galvanised duct transition

Round / Rectangular Duct Converter

Try practical widths and heights quickly while keeping equal or greater free area.

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Round fire damper installation in masonry on site

Fire Damper Opening Calculator

Manufacturer-specific openings and setting-out chains with official source links.

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Original site knowledge

Guides behind the calculations

Written from more than 18 years of ventilation installation experience—not generic trade summaries.

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Measure a straight or rolled offsetUse matching centrelines, combine rise and sideways movement, then remove both bend take-offs. Understand bend take-offWhy a centreline-radius rule does not replace the published dimension of a finished fitting. Set out a fire damper openingKeep nominal duct, casing, clearance, lining and the structural hole as separate stages. Change duct shape responsiblyCompare equal area, practical dimensions and aspect ratio before requesting approval.

Project records

Keep checked damper results together

Save results by tag and location, then reopen them or produce a Site Instruction Sheet.

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Built from more than 18 years on ventilation sites

VentTools is maintained by a Northern Ireland duct fitter, uses original site photographs and keeps manufacturer-specific fire-damper methods linked to their controlling sources.

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