3D Print Time Estimator: How Long Will It Take? (No Slicing Required)

A customer messages you on Etsy: “How fast can you have this ready?” They’ve attached an STL. You haven’t opened your slicer in two days. You need a number — close enough — without breaking your current print job to slice and check.

This guide gives you that number. Three quick formulas (by weight, by volume, by features) that get you within ±15% of what the slicer would say, in 30 seconds. Plus the settings that matter most when you DO have time to slice properly.

Quick estimate by weight (the 30-second method)

If you know the part weight in grams from the slicer or a similar previous print:

print_time_hours ≈ weight_grams ÷ 15  (modern fast printers)
print_time_hours ≈ weight_grams ÷ 10  (older or smaller printers)

Examples for a 50-gram PLA print:

Printer class	Calc	Estimated time
Bambu P1S / X1C (modern fast, 200-300mm/s)	50 ÷ 15 = 3.3	~3 hours
Prusa MK4S (modern, 150mm/s typical)	50 ÷ 12 = 4.2	~4 hours
Creality K1 (fast)	50 ÷ 14 = 3.6	~3.5 hours
Ender 3 V3 SE (budget, 60-100mm/s)	50 ÷ 8 = 6.3	~6 hours
Original Ender 3 / similar (50mm/s)	50 ÷ 6 = 8.3	~8 hours

These assume PLA at 0.20mm layer height, 15% infill, standard speed profile. For other materials and settings, see adjustments below.

Quick estimate by volume (when you only have CAD)

If you have a CAD volume in cm³ but haven’t sliced yet:

weight_grams ≈ volume_cm3 × 1.24 × (infill% + 0.15)

The (infill% + 0.15) accounts for the perimeter walls + top/bottom layers that get fully filled regardless of infill setting. So a part with 15% infill is actually about 30% solid by weight (15% infill volume + 15% wall/skin).

Example: 40cm³ part at 20% infill in PLA:

• weight ≈ 40 × 1.24 × (0.20 + 0.15) = 40 × 1.24 × 0.35 = 17.4 grams
• Then: 17.4 ÷ 15 = 1.16 hours on a modern fast printer

Adjustments by material

PLA is the speed baseline. Other materials add time because of slower recommended speeds:

Material	Speed factor	Adjustment
PLA	1.0×	(baseline)
PETG	1.4×	50g part: 3h PLA → 4.2h PETG
ABS / ASA	1.5×	50g: 3h → 4.5h
TPU 95A	2.5×	50g: 3h → 7.5h (very slow)
Nylon (PA)	1.6×	50g: 3h → 4.8h
Polycarbonate	1.5×	50g: 3h → 4.5h
PLA-CF / PETG-CF	1.2×	Slower than base material because of abrasive nozzle effect

Adjustments by layer height

Layer height has a more-than-linear effect on print time because of acceleration profiles:

Layer height	Time multiplier vs 0.20mm
0.08mm (very fine)	2.5×
0.10mm (fine detail)	2.0×
0.12mm (detail)	1.6×
0.16mm (default Bambu)	1.25×
0.20mm (default, baseline)	1.0×
0.24mm (faster)	0.83×
0.28mm (fast functional)	0.71×
0.32mm (max for 0.4mm nozzle)	0.625×

A 50g print at 0.20mm = 3.3 hours on a fast printer. Same print at 0.12mm = 5.3 hours. Same print at 0.32mm = 2.1 hours.

Adjustments by infill

Infill matters but less than people think because the perimeter walls and top/bottom layers are fixed regardless:

Infill	Time multiplier
5% (lightweight cosmetic)	0.92×
10% (default light)	0.94×
15% (standard default)	1.0× (baseline)
20% (light functional)	1.05×
30% (functional)	1.10×
50% (heavy functional)	1.20×
80% (near solid)	1.40×
100% (solid)	1.55×

Going from 15% to 50% infill is only +20% print time but doubles the material weight. So infill is “cheap” in time but expensive in filament cost. For most products, 15% is fine.

What slicer settings matter MOST for print time

Ranked by impact on a typical 50g print:

1. Print speed (outer wall, infill, travel) — 2-3× difference between conservative and aggressive
2. Layer height — 2.5× difference between 0.08mm and 0.32mm
3. Acceleration / jerk — 1.5× difference between low and high (modern printers handle high values fine)
4. Number of walls/perimeters — 3 walls vs 2 = +15% print time but much stronger
5. Top/bottom layer count — 4 vs 6 layers = +5% time
6. Infill density — typically only +5-20%
7. Cooling fan speed — minor impact (mostly affects first 5 layers)

For a faster print, change in this order: bump speed, increase layer height, raise acceleration. Other settings have marginal time effect.

Quick reference card — estimate by part size

For a quick mental model on a Bambu P1S / X1C / equivalent modern printer:

Part size	Typical weight	Print time
Small (60mm tall, simple)	15-30g	1.5-2.5 hours
Medium (100mm tall, moderate detail)	50-80g	3-5 hours
Large (180mm tall, full plate)	150-300g	8-15 hours
Multi-color (50g effective + 30g purge)	80g total	5-7 hours (purge waste adds time too)
Mini / miniature (28mm scale)	5-10g	30-60 minutes
Phone case	20-30g	2-3 hours
Vase mode (single wall)	30-50g	1-2 hours (much faster, single perimeter)

When the estimate matters and when it doesn’t

Where ±15% accuracy is fine:

• Quoting custom orders (“about 5 hours” tolerates 4-6h)
• Scheduling print farm jobs (“starts today, ships tomorrow”)
• Customer communication (“ready by Tuesday”)
• Project planning (“3 prints × 5 hours each = 15 hours”)

Where you need to actually slice:

• Production runs where 15% × 100 units = real money in machine time
• Time-critical deadlines (next-day shipping)
• Multi-material AMS prints where purge time is significant
• Multicolor prints (purge volumes vary wildly by color matrix)

The cost angle (this is where it actually matters)

Print time isn’t just a delivery question — it’s a cost question. Every minute of print time uses electricity, accumulates printer wear (depreciation), and ties up a machine that could be running other jobs.

A 50g print at 4 hours on a $700 printer over 6,000 hours of lifetime:

• Material (50g × $20/kg): $1.00
• Electricity (130W × 4h × $0.16/kWh): $0.08
• Depreciation: $0.47
• Labor (10 min @ $20/hr): $3.33

Total true cost: $4.88 — and 70% of that is time-driven, not material-driven. Doubling the print speed (cutting time to 2 hours) cuts depreciation in half AND lets you run another job in the same window.

For the full pricing math on this, the Pricing Calculator factors print time into electricity, depreciation, and labor cost lines automatically. Plug in the time estimate from this article and you get a complete cost number in 30 seconds.

Print speed economics

If you’re running a print farm, the case for upgrading to a faster printer is mostly about throughput:

• Old Ender 3 (60mm/s): 8 prints per day per machine
• Modern Bambu / Creality (250mm/s): 24+ prints per day per machine
• 3× throughput on the same labor cost = the economics that justified the Bambu P1S becoming the print-farm default

A $700 Bambu P1S paying for itself takes <1 month for a busy seller. The math is in the speed, not the print quality (both produce equivalent quality at default settings).

Common questions

Why is my estimate off? Two likely causes: print speed is way different from typical (very slow or very fast), or your slicer is using non-default settings (slower perimeters, more walls, lower acceleration). Open the slicer once to verify your typical profile matches the assumptions.

What about supports? Add 10-30% to the print time. Heavy support material adds proportionally more.

What about multicolor / AMS prints? Add 1-3 minutes per color change for purging. A 4-color print with 100 swaps adds 100 minutes — that’s significant. For accurate estimates on multicolor, you really do need to slice.

Do faster printers always print faster? Mostly. The speed limit is usually the printer’s acceleration capability, not the nozzle. Modern CoreXY printers (Bambu, Voron) accelerate faster than bedslingers (Ender, Prusa MK4). On simple prints, the speed advantage is 2-3×. On complex prints with lots of small features, the advantage narrows to 1.5× because acceleration time eats into the speed gains.

Use the estimates

These formulas get you a 30-second answer that’s right within ±15%. For tighter accuracy, slice. For commercial quoting, slice + add a 20% margin. For pricing math, see the Pricing Calculator which factors time into all the cost lines.