An ERA calculator computes a baseball pitcher's Earned Run Average (ERA) — the number of earned runs a pitcher allows per nine innings — and visualizes how ERA changes with different inputs.

Introduction
A clear, accessible ERA calculator helps coaches, analysts and fans quickly translate pitching performance into the familiar ERA metric. This tool is built for WordPress as a responsive custom HTML block. It accepts innings pitched and earned runs, converts common inning formats, computes ERA using the standard formula (ERA = earned runs × 9 ÷ innings pitched), and renders an interactive Plotly chart that illustrates how your inputs compare to plausible ranges. The calculator uses a white background and a compact, centered container so it fits between two sidebars without overflow.

How the calculator works
The calculator accepts two input styles: a decimal innings field (for shorthand like 7.2, where .1 = one out and .2 = two outs) or separate innings and outs fields. The script converts shorthand decimals to true innings (e.g., 7.2 becomes 7 + 2/3 = 7.6667 innings) so the ERA calculation is accurate. It validates inputs to avoid division by zero or negative values, displays the numeric ERA rounded to two decimal places, and updates an interactive Plotly chart in real time.

Why visualization matters
A single ERA number is useful, but the interactive graphic reveals sensitivity. One extra earned run in a short outing can spike ERA dramatically; over long workloads, the same run has a smaller effect. The Plotly line shows ERA as earned runs vary across a sensible range (0–15) for the innings you entered, and places a highlighted point at your entered earned runs to show where your ERA sits on that curve. That immediate visual feedback helps users understand context and volatility.

Using the calculator — step by step

1. Enter innings: Use the decimal shorthand (7.2) or fill innings and outs separately. If using the shorthand, remember .1 = one out (1/3 inning) and .2 = two outs (2/3 inning). The calculator converts both formats automatically.
2. Enter earned runs: Type the total earned runs allowed in the outing(s). Whole numbers are typical but decimals are accepted for aggregated stats.
3. Click Calculate or allow live updating: The ERA appears beneath the inputs with the exact formula and the computed numeric result (two decimal places).
4. Explore the chart: The Plotly chart displays ERA on the vertical axis and earned runs on the horizontal axis for your innings pitched. Drag, zoom, and hover to read exact values. The highlighted marker shows your input-derived ERA and is annotated for clarity.
5. Compare scenarios: Change innings or runs to see how ERA responds. To aggregate outings, sum earned runs and innings first and enter totals.

Design considerations for WordPress
The calculator is sized to fit a typical content column: a responsive container that is width:100% with max-width:760px. That keeps it centered between sidebars without overflowing. The white background and subtle padding let it blend with most themes. External dependencies are loaded via CDN to keep installation simple: paste the HTML/JS into a Custom HTML block or equivalent widget.

Accessibility and validation
Inputs include labels and aria attributes for screen readers. Numeric fields are validated to avoid nonsensical values. Error messages appear inline and are styled clearly. The Plotly chart includes axis labels and hover text so assistive technology users can extract the same information.

Plotly details and customization
Plotly is used for responsive interactive rendering. The script builds a line of ERA values for earned runs between 0 and a maximum (default 15), calculates ERA = 9*ER/innings for each point, then plots that line alongside a highlighted scatter point at your actual earned runs. You can customize the range, add reference lines, or export the chart as PNG via Plotly’s menu.

Practical tips and interpretations

• Small sample caution: ERA is unreliable on few innings. A single bad outing can skew the number. Use the chart to see volatility.
• Conversion clarity: If you track innings as outs, convert to decimal innings (3 outs = 1 inning) before comparisons; the tool does this if you enter outs separately.
• Aggregation: For seasonal statistics, sum earned runs and total innings across games, then calculate ERA from aggregated totals to avoid misrepresentation.
  Tip: Use the calculator during scouting or postgame review to instantly compare a single outing against season-level performance; toggling innings and runs highlights how marginal changes affect longer-term metrics and decision-making. use it wisely.

Installation instructions (quick)

1. Open WordPress Editor and add a Custom HTML block where you want the calculator.
2. Paste the HTML/JS code provided above into that block.
3. Save and preview. The calculator will size to the page column and render the Plotly chart.

Security and performance
The calculator is client-side only, so no server calls are required. External assets are limited to Plotly’s CDN. For heavy traffic sites, consider hosting Plotly locally or caching assets. All computations happen in the user’s browser, so no personal data leaves the site.

Conclusion
This ERA calculator combines a precise calculation with an instant visual to help you understand pitching performance quickly and accurately. Its responsive layout and WordPress-friendly sizing mean you can drop it into your site with minimal fuss, and Plotly ensures the visualization is interactive and informative.

FAQ
Q: What exact formula does the calculator use?
A: ERA = (Earned Runs × 9) ÷ Innings Pitched.

Q: How do I enter 7 and two outs?
A: Enter 7.2 in the innings field (the tool converts .2 → 2 outs = 2/3 inning) or enter 7 innings and 2 outs separately.

Q: Can I use this for multiple games?
A: Yes. Aggregate earned runs and innings across all games and enter totals; the output is the combined ERA.

Q: Is the chart exportable?
A: Yes — Plotly’s modebar includes download options like “Download plot as a png”.

Q: Does it require plugins?
A: No. Paste the provided HTML/JS into a Custom HTML block and it runs client-side.