# Media Fill Contamination Rate and Confidence Limit Calculator > Source: https://netray.co/tools/pharma-media-fill-contamination-rate-confidence-calculator > Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems. > Section: Free Tools ## Short answer Enter units filled and contaminated units from an aseptic process simulation to get the contamination rate and the 95% upper confidence limit. ## Category quality ## Industry Pharma and Life Sciences ## Audience - QA aseptic - Validation engineer - Sterile manufacturing ## Tool **Kind:** calculator **Inputs:** #### Units filled and incubated **Key:** filled **Type:** number **Default:** 5000 **Min:** 1 **Step:** 100 **Unit:** units **Help:** Total units filled in the media fill run and incubated. #### Contaminated units **Key:** contaminated **Type:** number **Default:** 0 **Min:** 0 **Step:** 1 **Unit:** units **Help:** Units showing microbial growth after incubation. #### Normal batch size **Key:** fill_size **Type:** number **Default:** 60000 **Min:** 1 **Step:** 1000 **Unit:** units **Help:** Used to compare run size against a normal batch. **Outputs:** #### Observed contamination rate **Key:** rate **Expr:** contaminated / filled * 100 **Format:** decimal **Description:** Percent of incubated units that were contaminated. #### 95% upper confidence limit (Wilson) **Key:** wilson_upper **Expr:** (contaminated / filled + pow(1.96, 2) / (2 * filled) + 1.96 * sqrt((contaminated / filled) * (1 - contaminated / filled) / filled + pow(1.96, 2) / (4 * pow(filled, 2)))) / (1 + pow(1.96, 2) / filled) * 100 **Format:** decimal **Primary:** true **Description:** Upper bound of the true contamination rate, in percent. #### Rule of three bound (zero growth only) **Key:** rule3 **Expr:** if(eq(contaminated, 0), 300 / filled, 0) **Format:** decimal **Description:** Approximate 95% upper bound when no units are contaminated. #### Upper limit per 10,000 units **Key:** per_10k **Expr:** wilson_upper * 100 **Format:** decimal #### Run size as share of a normal batch **Key:** run_share **Expr:** filled / fill_size * 100 **Format:** percent **Chart:** #### 95% upper limit vs units filled (at the contaminated count entered) **Type:** line **X:** filled **From:** 1000 **To:** 60000 **Steps:** 30 **Series:** - wilson_upper **Disclaimer:** Statistical illustration only. Acceptance criteria and investigation triggers come from your approved procedures and applicable regulations such as EU GMP Annex 1 and FDA aseptic processing guidance. ## Content **Intro:** A media fill (aseptic process simulation) proves that your people, environment and process can fill sterile units without introducing microbes. This calculator turns the raw counts into a contamination rate and a 95% upper confidence limit so you can see what a given run size can actually demonstrate. **Sections:** #### How to use it **Body:** Enter the number of units filled and incubated and the number showing growth. The Wilson interval is shown because it behaves properly when the count is zero or small, where the simple normal approximation fails. Use the chart to see how the demonstrable upper limit falls as run size increases. Then compare the result with the criteria in your approved protocol. **Bullets:** - Count units after the full incubation period. - Include every unit filled, not only inspected-good units, if your protocol requires it. - Record growth identifications for any positive unit. #### The method behind the numbers **Body:** The observed rate is contaminated divided by filled. The Wilson score upper bound uses z = 1.96 for two-sided 95% coverage. With zero positives the bound reduces to roughly 3.84 / (n + 3.84), close to the well known rule of three (3 / n). A 5,000 unit run with zero growth only supports an upper limit near 0.08 percent, which is why regulators expect zero growth as a target rather than a statistical allowance. #### Reading the result and common mistakes **Body:** A low observed rate from a small run can hide a real problem, so treat the confidence limit as the honest number. Do not use the calculator to justify accepting a positive unit. Any contaminated unit triggers an investigation under your quality system. Typical mistakes include mixing units from different simulations, ignoring interventions that were not simulated, and using a run size smaller than the largest line configuration. **Cta:** Netray can pull media fill results and environmental monitoring records from your ERP or QMS into one review view, running on your own servers. Ask for an expert review if you want that for your site. **Faq:** #### What is the acceptance criterion for a media fill? **Answer:** Current EU GMP Annex 1 expects zero growth as the target, with any contaminated unit investigated. Older guidance allowed small positive counts for large runs. Always follow your approved protocol and the regulations that apply to your market and product. #### Why use the Wilson interval instead of a simple proportion? **Answer:** When the count is zero or very small, the normal approximation gives a zero width interval, which is misleading. The Wilson interval stays valid at the extremes and never goes below zero or above one. #### How many units should a media fill include? **Answer:** Run size should reflect the largest batch size and line, with enough units to support a meaningful upper limit. Many sites fill several thousand units or the full batch size for small lots, but your protocol and risk assessment decide. #### Does this replace validation statistics software? **Answer:** No. It is a quick sizing and reporting aid. Formal protocol approval, deviation handling and trending belong in your quality system and validated tools. ## Search terms media fill calculator, aseptic process simulation acceptance criteria, media fill contamination rate, media fill number of units, annex 1 media fill, media fill confidence limit, APS media fill sample size --- Talk to an engineer: https://netray.co/contact?intent=erp_ai | Machine catalog: https://netray.co/agent/catalog.json