3D Printer Actual Speed Calculator
Enter a straight feature length, its planned speed, and the speeds at each end to see whether the printer can actually reach that speed. The result also shows the distance and time spent accelerating, cruising, and decelerating.
Peak speed reached (mm/s)245.76
- Requested speed reached?
- No
- Motion profile
- Triangular
- Acceleration distance (mm)
- 10
- Cruise distance (mm)
- 0
- Deceleration distance (mm)
- 10
- Move time (seconds)
- 0.15
- Average speed (mm/s)
- 132.88
- Target speed utilization
- 81.92%
- Minimum length to reach target (mm)
- 29.87
- Required proportional acceleration (mm/s²)
- 4,480
- Required proportional deceleration (mm/s²)
- 4,480
Uses ideal constant acceleration and deceleration along one straight move.
The reverse-solved values preserve the entered acceleration-to-deceleration ratio.
How to use this calculator
- Enter the straight-line distance available for the move or printed feature.
- Enter the requested slicer speed and the entry and exit speeds set by nearby corners.
- Enter the effective acceleration and deceleration used for this kind of move.
- Compare the peak and average speeds with the requested speed, then use the reverse result if the target does not fit.
How actual speed is calculated
A printer cannot jump from a corner speed to the speed selected in the slicer. It needs distance to gain speed and, before the next corner, distance to lose it again. On a short line the printer may begin slowing down before it ever reaches the requested speed.
Let L be the available length, V the requested speed, u the entry speed, w the exit speed, a the acceleration, and d the deceleration magnitude. The length needed to reach the target is:
Lrequired = (V² − u²) / (2a) + (V² − w²) / (2d)
When that length fits, the peak speed is V and the remaining distance is travelled at a constant speed. This is a trapezoidal profile. When it does not fit, the calculator solves for the lower peak:
P = √((2adL + du² + aw²) / (a + d))
That is a triangular profile: acceleration changes directly to deceleration with no cruise section. The acceleration and deceleration distances come from (P² − u²) / (2a) and (P² − w²) / (2d). Move time is the acceleration time, plus any cruise time, plus the deceleration time. Average speed is the feature length divided by that total time.
What changes the result most
Feature length and acceleration usually matter more than the slicer speed on small walls, infill strokes, and patterned perimeters. Higher entry and exit speeds also reduce the amount of velocity change required, but they depend on the next moves and on firmware cornering limits. Use the entry and exit figures that your firmware can carry through those corners, rather than assuming every move starts and ends at zero.
The proportional reverse result answers a narrower question: what pair of acceleration and deceleration limits would just let this move reach the requested speed while keeping their current ratio. If the target already fits, those are minimum theoretical values, not recommended settings.
What this calculator leaves out
This is an ideal constant-acceleration model. It does not simulate input shaping, pressure advance, jerk-limited motion, firmware look-ahead, extrusion flow limits, or slicer path planning. A print also contains corners, travel moves, cooling, heating, and firmware overhead, so this one-move time is not a full print-time estimate.
Worked example
Consider a 20 mm line requested at 300 mm/s, entering and leaving at 20 mm/s, with 3,000 mm/s² acceleration and deceleration. Reaching 300 mm/s would need (300² − 20²) / (2 × 3,000) on each side, or 14.93 mm + 14.93 mm = 29.87 mm. The target therefore does not fit.
The triangular calculation gives a peak of 245.76 mm/s. It spends 10 mm accelerating and 10 mm decelerating, with no cruise distance. The move takes about 0.15 seconds, so its average speed is 132.88 mm/s. Preserving the equal acceleration and deceleration ratio, reaching 300 mm/s in 20 mm would require about 4,480 mm/s² in both directions.
Common questions
Why does my printer never reach the speed selected in the slicer?
Many print moves are too short to accelerate to the requested speed and then slow for the next corner. The slicer speed is a cap, not a guarantee. Lower acceleration, low corner speeds, and short segments reduce the actual peak still further.
How much distance does a printer need to reach 300 mm/s?
It depends on entry speed, exit speed, acceleration, and deceleration. At 3,000 mm/s² with 20 mm/s at both ends, the tool calculates about 29.87 mm. Faster corner speeds or higher acceleration reduce that length.
What is the difference between a triangular and trapezoidal velocity profile?
A trapezoidal profile has acceleration, a constant-speed cruise section, and deceleration. A triangular profile has no cruise section because the move is so short that the printer starts decelerating as soon as it reaches its peak speed. Both descriptions refer to the speed-versus-time graph.
How do corner speed and square-corner velocity affect the result?
They determine the speed a printer can carry into and out of a segment, represented here by entry and exit speed. Higher allowed corner speed can improve average speed on connected lines, but it can also increase ringing and mechanical load. Firmware look-ahead may choose different values across a real path.
Does higher acceleration always reduce print time?
Higher acceleration reduces the time spent changing speed and is most noticeable on short features. It does not make a long, already cruising move exceed its requested speed. Excessive acceleration can cause ringing, missed steps, layer shifts, or extrusion problems, so it must be validated on the printer.
Why is average print speed much lower than peak speed?
Peak speed is reached only briefly on many features, while the printer spends substantial time accelerating and decelerating. Corners and low entry or exit speeds reduce the average again. The average shown here applies only to the entered straight move.