Tolerance Stackup Calculator
Estimate tolerance stackup for your project with our free calculator. Get accurate material quantities, costs, and specifications.
Formula
RSS Stackup = sqrt(t1² + t2² + t3² + ... + tn²)
The RSS (Root Sum of Squares) method calculates the statistical tolerance stackup by taking the square root of the sum of the squares of each individual tolerance. This assumes part dimensions follow a normal distribution and tolerances are independent. For worst-case, simply sum all tolerances. For statistical analysis, multiply RSS by Z/3 where Z is the Z-score for the desired confidence level.
Frequently Asked Questions
What is tolerance stackup analysis?
Tolerance stackup analysis is the process of calculating the cumulative effect of individual part tolerances on an overall assembly dimension. When multiple parts are assembled together, each part contributes its own tolerance variation, and these variations can add up to produce a total assembly variation that may exceed acceptable limits. Engineers use stackup analysis during the design phase to ensure that assembled components will fit and function correctly.
What is the difference between worst-case and RSS stackup?
Worst-case (arithmetic) stackup assumes every part is simultaneously at its maximum or minimum tolerance limit, which is extremely unlikely in real production. RSS (Root Sum of Squares) stackup uses a statistical approach, calculating the square root of the sum of squared tolerances. RSS typically yields a stackup 40-60% smaller than worst-case because it accounts for the statistical probability that not all parts will be at their extremes simultaneously. RSS assumes a normal distribution of part dimensions.
How does the confidence level affect statistical tolerance stackup?
The confidence level determines what percentage of assemblies will fall within the calculated tolerance range. A 99.73% confidence (3-sigma) means only 2,700 out of 1 million assemblies might fall outside limits. Higher confidence levels like 99.99% (approximately 3.89-sigma) produce wider tolerance bands but fewer rejects. The statistical stackup equals the RSS value multiplied by the Z-score divided by 3. For most manufacturing, 99.73% (3-sigma) provides a good balance between tight tolerances and acceptable reject rates.
Is Tolerance Stackup Calculator free to use?
Yes, completely free with no sign-up required. All calculators on NovaCalculator are free to use without registration, subscription, or payment.
Does Tolerance Stackup Calculator work offline?
Once the page is loaded, the calculation logic runs entirely in your browser. If you have already opened the page, most calculators will continue to work even if your internet connection is lost, since no server requests are needed for computation.
Is my data stored or sent to a server?
No. All calculations run entirely in your browser using JavaScript. No data you enter is ever transmitted to any server or stored anywhere. Your inputs remain completely private.