Additive manufacturing / FFF planning

3D Printing Volumetric Flow & Build Time Estimator

Calculate requested extrusion flow, hotend utilization, maximum speed at a flow limit, and a planning-level build-time estimate.

01 / Engineering inputs

Live calculation

Extrusion line width

Use the slicer’s actual extrusion width for the feature being checked.

Layer height

Uses the PrusaSlicer-style rounded-rectangle cross-section; width must be at least the layer height.

Requested print speed

Nominal extrusion move speed, excluding travel.

Hotend volumetric-flow limit

Use a tested limit for the filament, temperature, nozzle, and hotend.

Estimated extruded material volume

Use slicer material volume, not the solid bounding volume of the model.

Travel and process-time allowance

Planning allowance for travel, acceleration, retraction, layer changes, and other non-extrusion time.

Formula, scope & sources

How this calculator works

Volumetric flow

Q = h × [w − h × (1 − π/4)] × speed

The non-bridge bead is modelled as a rectangle with semicircular ends, matching PrusaSlicer’s rounded-rectangle cross-section.

Planning time

Time ≈ material volume / effective flow × (1 + allowance)

Effective flow is capped at the entered hotend limit. A slicer or parsed G-code remains the better source for production scheduling.

Production application disclaimerThe build-time result is an estimate, not a slicer replacement. Real duration depends on toolpaths, acceleration, travel, retractions, cooling, minimum layer time, feature-specific speeds, flow dynamics, firmware, and machine limits. Validate final scheduling with sliced G-code.

Reference basis: Prusa maximum-volumetric-speed reference · PrusaSlicer rounded-rectangle flow implementation · PrusaSlicer G-code time estimator

Implementation: Original MfgWorkbench calculation code, independently verified against cited formulas and worked examples. Last reviewed September 4, 2026.

Separate requested flow from the hotend limit

The calculator checks one extrusion condition, then estimates time at the lower of requested flow and your entered limit. A result below 100% utilization is not a validated printer profile. Use a tested limit for the actual filament, temperature, nozzle and hotend.

Links load hypothetical inputs, switch to metric and recalculate. Read the capped-flow example · Understand the time estimate. Without JavaScript, the worked calculations below remain readable.

Follow one set of slicer inputs through the calculation

Select metric units and enter line width 0.45 mm, layer height 0.20 mm, print speed 60 mm/s, an illustrative hotend limit of 6 mm³/s, extruded volume 20 cm³ (20,000 mm³) and allowance 25%. These are example inputs, not a tested printer profile.

Step	Expected result
Rounded bead area: 0.20 × [0.45 − 0.20 × (1 − π/4)]	0.08141593 mm²
Requested flow: area × 60	4.884956 mm³/s
Speed at entered flow limit: 6 / area	73.69565 mm/s
Flow utilization: requested flow / 6	81.41593%
Extrusion-only time: 20,000 / 4.884956	4,094.203 s = 1.137279 h
With 25% allowance	1.421598 h

Which slicer values should you copy?

Use the extrusion width and speed for the feature being checked, not automatically the nozzle diameter or the fastest travel speed. Use material actually extruded, including supports and purge if relevant, rather than the model’s solid bounding volume. Obtain the applicable volumetric limit from a verified profile or controlled flow test for that filament, temperature, nozzle and hotend.

For a real job, save the slicer’s predicted time beside this estimate and then record actual elapsed time. Differences expose the effect of acceleration, cooling and feature-specific speeds. No real printer or G-code comparison is claimed for the arithmetic example above.

What changes when requested flow is too high?

Load the flow-limited example: width 0.60 mm, height 0.30 mm, speed 200 mm/s, limit 18 mm³/s, volume 18 cm³ and allowance 0%. Rounded bead area is 0.16068583 mm², so requested flow is 32.13717 mm³/s, or 178.5% of the entered limit. Speed at that limit is approximately 112.02 mm/s.

The time calculation uses 18 mm³/s, not 32.13717: 18,000 ÷ 18 = 1,000 seconds = 0.277778 hours. At 0% allowance the planning and extrusion-only times are equal. The calculator does not change your printer or slicer settings; reduce the relevant extrusion speeds or otherwise validate the profile yourself.

Original comparison using this page’s capped-flow example. The shorter bar is the effective flow used in the time estimate.

Read the two time outputs correctly

Extrusion-only time assumes all entered material is deposited at one effective flow. Planning build time adds the percentage allowance. Neither is a toolpath simulation: small perimeters, cooling limits, acceleration and travel can dominate an actual print. If the slicer already supplies a detailed job time, do not add this allowance to it automatically.

Is extrusion width the nozzle diameter?

No. Copy the actual width for the feature from your slicer. This rounded-rectangle model requires width at least equal to layer height and applies to supported, non-bridge extrusion. Bridges need different geometry.

What volume and units should I enter?

Metric material volume is cm³, while flow is mm³/s; 1 cm³ = 1,000 mm³. Use extruded material, including support or purge where applicable, not the model’s bounding box. The Imperial switch converts volume to in³ and flow to in³/s; time remains in hours.

Calculator and examples reviewed October 19, 2026. Numerical verification is not a printer test, a calibrated hotend limit or a guaranteed completion time. Editorial method · Report a correction.