Offset IQ

advanced offset smoker calculator

Advanced smoker design calculator with differential ratios, airflow modes, and comprehensive build specifications.

Cook Chamber

Enter your cooking chamber dimensions

Diameter

inches

Length

inches

Chamber Volume

—in³

Volume (Gallons)

—gal

Effective Width

—inches

Firebox

Enter inner firebox dimensions. Optionally enable insulation for outer dimension calculation.

Insulated Build

Calculate outer dimensions with insulation

Inner Height

Inner Width

Inner Length

Your Firebox

—in³

Recommended

—

(approx cubic)

Differential

—

Chimney / Stack

Enter stack dimensions to calculate recommended length based on Classic Offset mode

Classic Offset Mode Active

Feldon's 5% firebox volume rule

Stack Diameter

inches

Stack Length

inches

Stack Area

—in²

Stack Volume

—in³

Recommended Length

—inches

Your Length

—inches

—

💡 Typical range: 30–48 inches. If using a vertical warming cabinet, reduce length as the cabinet acts as additional stack.

Collector / Exhaust Plenum

Configure your exhaust collector type and dimensions

Collector Type

Direct stack connection without collector

Differential Ratios & Airflow

Configure airflow mode and review calculated differential ratios

Airflow Mode Preset

Throat-to-Stack Ratio100% of stack area

80% (Restricted)100% (Balanced)130% (Open)

RF Plate Gap Ratio105% of throat area

90% (Tight)105% (Standard)120% (Open)

Throat Area

—in²

—

RF Gap Area

—in²

RF Gap Height

—inches

Based on —" width

Throat Diameter

—inches

Round opening

Air Intakes

Configure your firebox air intake vents

Number of Intakes

How many intake vents?

Diameter per Vent

inches

Recommended Total

(75% of stack area)

—in²

Per Vent Target

—in²

Your Total Area

—in²

Status

—

Airflow Dynamics

Classic Offset

Flow Speed

Medium

Flow Pattern

Balanced

Intake

Restricted

Exhaust Draw

Weak

Convection Score

5.0

/10

Fair

Air Intake

5.0

Exhaust Draw

5.0

Throat Design

5.0

Stack Efficiency

5.0

Fuel Efficiency

5.0

Fair convection. The smoker will function, but consider optimizing intake area, stack dimensions, or throat design for better performance.

Summary Report

Complete design specifications and diagnostics

Looking good

Classic Offset

Your design is well-balanced. All major components are within recommended ranges.

Cook Chamber

Volume— in³

Gallons—

Width—"

Firebox

Your Size— in³

Target (33%)— in³

Differential—%

Collector

Area— in²

Stack Ratio—×

Draw Score—/10

Throat & RF Gap

Throat Area— in²

Throat Ø—"

RF Gap Height—"

Chimney

Stack Area— in²

Rec. Length—"

Your Length—"

Air Intakes

Target Total— in²

Per Vent— in²

Round Ø—"

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