I Built a Crypto Passive Income Calculator. The Math Surprised Even Me.

I wanted to see four crypto passive income methods compared side by side with real dollar outputs. Not APY percentages — actual portfolio values based on my capital and time horizon.

Every calculator I found was single-method. ETH staking only. Or DeFi APY only. Nobody had built the comparison I wanted.

So I built it.

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What It Does

Forward mode — you put in capital ($500 to $1M+), select a time horizon (1-10 years), toggle compounding on or off. Four methods update simultaneously:

— ETH Staking (3.5% APY current rate)
— DeFi Lending (6% APY Aave/Compound average)
— Copy Trading (~25% avg retail)
— Endotech AI (163% avg annual — 8yr institutional record)

You get total portfolio value, monthly profit, percentage gain, a Chart.js growth line chart, and a year-by-year breakdown table.

Goal/Reverse mode — the feature that makes people stop. Enter a target monthly income. The calculator tells you how much capital each method requires to hit that number.

The output that gets screenshots:

Target: $1,000/month

ETH Staking:          $343,000 needed
DeFi Lending:         $200,000 needed
Copy Trading:         $48,000 needed
Endotech AI (net):    $7,362 needed

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The Tech Stack

Vanilla JS. No frameworks. Chart.js 4.4.0 for the growth visualization. Tailwind CDN (preflight disabled) for layout. Everything in a single HTML file.

The main calculation functions:

function calcValue(principal, rate, yrs, compound) {
  if (compound) {
    return principal * Math.pow(1 + rate, yrs);
  } else {
    return principal + (principal * rate * yrs);
  }
}

const RATES = {
  staking: 0.035,   // ETH current APY
  defi: 0.06,       // Aave/Compound USDC avg
  copy: 0.25,       // Retail copy trading generous avg
  ai: 1.63          // Endotech BTC Alpha 8yr avg
};

Goal mode is just the inverse:

// How much capital to hit monthly income target
const annualGoal = monthlyTarget * 12;
const needed = annualGoal / rate;

// Endotech after 50% performance fee:
const neededAI = annualGoal / (RATES.ai * 0.5);

The share buttons generate dynamic text pulling the user's actual results:

function getShareText() {
  var aiResult = document.getElementById('ai-result').textContent;
  var stakingResult = document.getElementById('staking-result').textContent;
  return 'Staking gives ' + stakingResult + '. ' +
         'Institutional AI gives ' + aiResult + '. ' +
         'The difference: https://limitlessibportal.io/...'
}

Seven share targets: X, LinkedIn, WhatsApp, Telegram, Facebook, Reddit, copy link.

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The Chart.js Gotcha in Estage CMS

One issue worth documenting: Chart.js renders at 0px height when loaded inside certain CMS environments because the parent container collapses before the canvas gets its dimensions.

The fix — load Chart.js async at the bottom of body with a polling fallback:

function loadChartJS() {
  var s = document.createElement('script');
  s.src = 'https://cdnjs.cloudflare.com/ajax/libs/Chart.js/4.4.0/chart.umd.min.js';
  s.onload = function() {
    var attempts = 0;
    function tryInit() {
      var canvas = document.getElementById('growthChart');
      if (!canvas) {
        if (attempts++ < 20) setTimeout(tryInit, 200);
        return;
      }
      var w = canvas.parentElement.offsetWidth || 700;
      canvas.width = w;
      canvas.height = 300;
      initChart();
      calculate();
    }
    setTimeout(tryInit, 300);
  };
  document.head.appendChild(s);
}
window.addEventListener('load', loadChartJS);
setTimeout(loadChartJS, 500); // Fallback if load already fired

The HTML attribute width and height on the canvas element also matter — Canvas ignores CSS dimensions for its drawing buffer without them:

<canvas id="growthChart" width="800" height="300"></canvas>

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The SEO Play

Beyond the tool itself this is a parasite SEO and link building asset. The goal mode number ($7,362 vs $343,000) is the shareable hook that drives organic backlinks from crypto passive income articles that have no calculator.

Target keywords: "crypto passive income calculator", "how much do I need to earn $1000 month from crypto", "eth staking calculator 2026".

Full tool live here: https://limitlessibportal.io/crypto-passive-income-calculator

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Disclaimer: The Endotech figures are based on 8-year historical performance. Past performance does not guarantee future results. Not financial advice.