A while back I wanted one number. What would my mortgage payment be if rates dropped half a percent? Simple question. Thirty seconds of maths, tops.
Here's what I got instead. A cookie banner with 47 toggles. A popup asking for my email before I'd typed anything. A page that jumped around three times while ads loaded, so I tapped the wrong thing twice. And above the actual calculator, ten paragraphs of filler explaining what a mortgage is, clearly written for a search engine rather than a human. The answer was in there somewhere. Eventually.
I closed the tab and thought, this shouldn't be hard. So I built the thing I wanted to use.
What I wanted
The list was short. Pages that load instantly. The calculator at the top, not buried under an essay. The formula shown, so you can check the working instead of trusting a black box. And no spying.
That last one matters more than people realise. On most calculator sites, you're typing in your salary, your debts, your savings. That's sensitive stuff. On EvenSums, every calculation runs in your browser. The numbers never leave your device. There's no server crunching your figures, no database quietly filling up with everyone's balances. I couldn't peek at your inputs even if I wanted to, which suits us both.
What launched
EvenSums went live in July 2026 with 25 calculators, covering loans, savings, mortgages, retirement and the everyday stuff in between. A couple I'm particularly pleased with:
The mortgage calculator, because it's the one that started all this. It gives you the payment straight away and shows how it splits between interest and principal, which is the part most people have never actually seen.
The Coast FIRE calculator, because it answers a question I find genuinely cheering: how much do you need invested now so that compounding alone carries you to retirement, even if you never save another penny? The answer is usually smaller than people expect.
What it's not
I'll be straight with you. The site is three weeks old. There will be rough edges. There may be bugs I haven't found yet, despite a lot of testing and a mild obsession with rounding. Some calculators will grow features, others might get rebuilt entirely once I see how people actually use them.
If you spot something wrong, or there's a calculator you wish existed, I'd honestly like to hear about it. There's a contact address on the about page. I read everything that comes in. Right now that's not a huge boast, but it's true.
The short version
I believe a calculator site should be fast, private and honest. Fast, because you came here for one number. Private, because your finances are your business. Honest, because you should be able to see the formula and check the maths yourself.
That's the whole pitch. No newsletter, no account, no popup asking you to rate your experience. Just sums, done evenly. Thanks for reading, and if the site saves you from even one cookie banner with 47 toggles, it was worth building.