{"tool":{"slug":"compound-interest","name":"Compound interest calculator","version":"2026-08-21","canonicalUrl":"https://carlo.finance/tools/compound-interest?principal=50000&monthly=500&years=30","jsonUrl":"https://carlo.finance/tools/compound-interest.json?principal=50000&monthly=500&years=30","pageUrl":"https://carlo.finance/tools/compound-interest","parameters":[{"key":"principal","label":"Starting amount","unit":"usd","min":0,"max":100000000,"default":10000,"sourceId":null,"help":"What you start with. The default is an example, not a statistic."},{"key":"monthly","label":"Monthly contribution","unit":"usd-per-month","min":0,"max":1000000,"default":250,"sourceId":null,"help":"Added at the end of each month. The default is an example; set it to zero to grow the starting amount alone."},{"key":"rate","label":"Annual return","unit":"percent","min":0,"max":20,"default":7,"sourceId":null,"help":"The yearly growth you assume, before taxes and fees. This is an assumption you choose, not a forecast; the default is an example to replace with your own."},{"key":"years","label":"Years to grow","unit":"years","min":1,"max":60,"default":20,"sourceId":null,"integer":true,"help":"How long the money compounds before you look at the balance."},{"key":"compounds","label":"Compounding per year","unit":"count","min":1,"max":365,"default":12,"sourceId":null,"integer":true,"help":"How many times a year interest is credited: 1 yearly, 12 monthly, 365 daily."}]},"inputs":{"principal":50000,"monthly":500,"rate":7,"years":30,"compounds":12},"result":{"endBalance":1015810.37,"totalContributed":230000,"growth":785810.37,"effectiveAnnualYield":7.229,"doublingYears":9.931,"months":360,"finalYearGrowth":68260.97,"yearly":[{"year":1,"contributed":56000,"growth":3810.8,"balance":59810.8},{"year":2,"contributed":62000,"growth":8330.82,"balance":70330.82},{"year":3,"contributed":68000,"growth":13611.33,"balance":81611.33},{"year":4,"contributed":74000,"growth":19707.31,"balance":93707.31},{"year":5,"contributed":80000,"growth":26677.71,"balance":106677.71},{"year":6,"contributed":86000,"growth":34585.75,"balance":120585.75},{"year":7,"contributed":92000,"growth":43499.19,"balance":135499.19},{"year":8,"contributed":98000,"growth":53490.73,"balance":151490.73},{"year":9,"contributed":104000,"growth":64638.3,"balance":168638.3},{"year":10,"contributed":110000,"growth":77025.47,"balance":187025.47},{"year":11,"contributed":116000,"growth":90741.85,"balance":206741.85},{"year":12,"contributed":122000,"growth":105883.53,"balance":227883.53},{"year":13,"contributed":128000,"growth":122553.54,"balance":250553.54},{"year":14,"contributed":134000,"growth":140862.37,"balance":274862.37},{"year":15,"contributed":140000,"growth":160928.48,"balance":300928.48},{"year":16,"contributed":146000,"growth":182878.92,"balance":328878.92},{"year":17,"contributed":152000,"growth":206849.9,"balance":358849.9},{"year":18,"contributed":158000,"growth":232987.48,"balance":390987.48},{"year":19,"contributed":164000,"growth":261448.29,"balance":425448.29},{"year":20,"contributed":170000,"growth":292400.27,"balance":462400.27},{"year":21,"contributed":176000,"growth":326023.52,"balance":502023.52},{"year":22,"contributed":182000,"growth":362511.13,"balance":544511.13},{"year":23,"contributed":188000,"growth":402070.18,"balance":590070.18},{"year":24,"contributed":194000,"growth":444922.69,"balance":638922.69},{"year":25,"contributed":200000,"growth":491306.76,"balance":691306.76},{"year":26,"contributed":206000,"growth":541477.67,"balance":747477.67},{"year":27,"contributed":212000,"growth":595709.18,"balance":807709.18},{"year":28,"contributed":218000,"growth":654294.84,"balance":872294.84},{"year":29,"contributed":224000,"growth":717549.4,"balance":941549.4},{"year":30,"contributed":230000,"growth":785810.37,"balance":1015810.37}]},"drivers":[{"key":"years","label":"Years to grow","step":5,"endDelta":460024.5199999999,"sentence":"Five more years of compounding adds $460,025 to the final balance."},{"key":"rate","label":"Annual return","step":1,"endDelta":276155.83999999997,"sentence":"One more point of assumed return adds $276,156 to the final balance."},{"key":"monthly","label":"Monthly contribution","step":100,"endDelta":121997.09999999998,"sentence":"Each $100 more a month adds $121,997 to the final balance."},{"key":"principal","label":"Starting amount","step":1000,"endDelta":8116.5,"sentence":"Each $1,000 more at the start adds $8,117 to the final balance."}],"sensitivity":{"byRate":[{"rate":4,"endBalance":512699.6,"growth":282699.6},{"rate":5,"endBalance":639516.53,"growth":409516.53},{"rate":6,"endBalance":803386.28,"growth":573386.28},{"rate":7,"endBalance":1015810.37,"growth":785810.37},{"rate":8,"endBalance":1291966.21,"growth":1061966.21},{"rate":10,"endBalance":2122113.93,"growth":1892113.93}],"byYears":[{"years":5,"endBalance":106677.71,"contributed":80000,"growth":26677.71},{"years":10,"endBalance":187025.47,"contributed":110000,"growth":77025.47},{"years":20,"endBalance":462400.27,"contributed":170000,"growth":292400.27},{"years":30,"endBalance":1015810.37,"contributed":230000,"growth":785810.37},{"years":40,"endBalance":2127977.27,"contributed":290000,"growth":1837977.27}]},"assumptions":[{"key":"principal","label":"Starting amount","value":50000,"unit":"usd","provided":true,"source":null},{"key":"monthly","label":"Monthly contribution","value":500,"unit":"usd-per-month","provided":true,"source":null},{"key":"rate","label":"Annual return","value":7,"unit":"percent","provided":false,"source":null},{"key":"years","label":"Years to grow","value":30,"unit":"years","provided":true,"source":null},{"key":"compounds","label":"Compounding per year","value":12,"unit":"count","provided":false,"source":null}],"sources":[],"warnings":[],"disclaimer":"This models deterministic compound growth at a rate you choose. It is not a forecast, a promised return, or investment advice. Real returns vary year to year and can be negative; taxes, fees, and inflation sit outside the model."}