Tolerance & Fit Calculator
Calculate expected dimensional tolerance, shrinkage compensation, and recommended clearances for 3D printed parts based on printer type and material.
About this calculator
A 3D printed part almost never comes out exactly the size it was modeled at, for two separate and independent reasons this calculator tracks separately: PROCESS tolerance (how precisely the printer itself can position and deposit or cure material) and MATERIAL shrinkage (how much the part physically contracts as filament cools or resin cures after printing). Process tolerance depends on printer type -- resin-based SLA/MSLA printers are typically the most dimensionally accurate, SLS falls in the middle, and FDM (fused deposition, the most common desktop printer type) has the widest tolerance band because layer adhesion and nozzle positioning introduce more variation. That tolerance also widens slightly as the part gets larger, since small positioning errors compound over a bigger span.
Material shrinkage is a completely separate effect: as plastic cools or resin cures, it physically contracts by a percentage of its size that depends only on the material (Nylon shrinks the most among the options here, PLA and tough resin the least). The calculator reports both effects plus practical outputs derived from them: a compensated design size (add shrinkage back in before you model the part) and recommended clearances for press, sliding, and loose mechanical fits.
Inputs
Results
Expected Tolerance (±)
0.31 mm
Shrinkage Amount
0.06 mm
How to Use This Calculator
- Select your printer type (FDM or resin SLA/MSLA) and filament or resin material.
- Enter the nominal design dimension (mm) that requires a precise fit.
- Review expected dimensional tolerance (±mm) and the resulting min/max dimension range.
- Use the compensated design size output to adjust your CAD model to achieve the target fit.
- Print a test coupon at the compensated size and measure before committing to final parts.
What each input means
- Printer Type
- Type of 3D printer being used. SLA is most precise, FDM is least precise.
- Material
- Print material. Different materials have different shrinkage rates as they cool or cure.
- Nominal Dimension
- The target dimension of the feature you are designing (e.g., hole diameter, peg width).
How this is calculated
Worked example, using the default values
- Identify Input ParametersPrinter Type = 1, Material = 1, Nominal Dimension = 20 = 3 input(s) provided
- Calculate Expected ToleranceExpected Tolerance0.31 = 0.31
- Calculate Shrinkage AmountShrinkage Amount0.06 = 0.06
- Calculate Minimum DimensionMinimum Dimension19.69 = 19.69
- Calculate Maximum DimensionMaximum Dimension20.31 = 20.31
Engine last updated . Checked against 2 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why does the printer type not affect the shrinkage compensation numbers?
Shrinkage happens as the printed MATERIAL cools or cures, which is a property of the plastic or resin itself, not of the machine extruding or curing it -- Nylon shrinks roughly the same percentage whether it's printed on one FDM printer or another. Printer type instead determines the separate dimensional TOLERANCE (how precisely the machine can position and deposit material), which is why this calculator keeps the two effects on independent inputs.
Why doesn't material choice change the expected tolerance figure?
Tolerance in this calculator reflects positioning and process precision -- how accurately the printer's mechanics can place material layer by layer -- which is determined by printer type, not by which plastic or resin is loaded. Material choice instead drives the separate shrinkage calculation, since different plastics contract by different amounts as they cool.
Does a larger nominal dimension always mean more shrinkage to compensate for?
Yes -- shrinkage amount scales directly with the nominal size, since it's calculated as the dimension multiplied by the material's shrinkage percentage. A 200mm feature in a material with 0.5% shrinkage will shrink about ten times more, in absolute millimeters, than a 20mm feature in the same material, even though the percentage is identical.
Which printer type gives the tightest tolerance for a precision-fit part?
Of the three options, SLA/MSLA resin printing carries the tightest base tolerance band in this calculator, reflecting resin printing's finer effective resolution compared to FDM's larger nozzle diameters and layer heights. SLS falls in between the two. For a part with a critical press or sliding fit, selecting SLA/MSLA here (if that's a real option for your project) will show the narrowest expected tolerance range.
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