NUMO

The Only UK App That Tells You If Premium Bonds Beat ISAs

Track your actual returns, compare ISAs, and finally know if you're lucky. Plus beautiful calculators for savings & mortgages.

Why We Built NUMO

The financial calculator landscape hasn't evolved in a decade. Premium Bonds? No app compares them to ISAs properly (21+ million UK holders are flying blind). Mortgages? The calculators either don't exist or look like they're from 2012. Savings? You're bouncing between 5 different apps.

Meet NUMO: one beautifully designed app delivering accurate, personalised answers—your way.


Features

Track Premium Bonds Like Never Before

See your actual returns. Compare ISAs. Discover if you're lucky. The only app that does this well.

Actual Returns

Log your holdings, track prize wins, see your real annual return %. Not averages. YOUR numbers.

ISA Comparison

What would an ISA at 3.5%, 4.5%, or 5.5% earn? Compare instantly. 

Lucky? Unlucky?

Know if you're beating the odds. See expected vs actual. Finally understand Premium Bonds.

Mortgages - See Exactly How Much You'll Save

Whether you're planning to overpay £100 or £1,000 monthly, our mortgage calculator shows the real impact.

Plan Your Savings. See Real Growth.

Whether you're saving for a goal or just watching your money grow, our AER calculator shows exactly what you'll have in 1, 5, or 10 years.

Built on Trust

Your Data is Yours

Everything works offline. No data sent to our servers. No tracking. No ads. Ever.

Calculation You Can Trust

We show you HOW we calculate. No black boxes.

Free To Try. Forever Free Tier.

All core calculators free. No credit card required.

Questions? We've Got Answers

Will NUMO cost money?

Yes, We're planning a premium tier later for advanced features (namely Amortization Schedule, NSI Premium Bonds tracking), but AER calculators stays free.

Is my data safe?

Absolutely. Your financial data and word lists never leave your device.

We collect only anonymous app usage stats to fix bugs and improve features. No personal data. No ads. No selling your info.

What data do you collect?

Your personal data stays on your device. We collect only anonymous analytics:

  • Device type and OS version
  • Which features you use (not what you enter)
  • Crash reports to fix bugs

We never collect your Premium Bonds holdings, financial calculations, or any personally identifiable information.

Do you share my data with third parties?

We never sell your data.

Your personal information (Premium Bonds, word lists, etc.) stays on your device and is never transmitted to us or anyone else. We use PostHog, a privacy-focused analytics service, to collect anonymous app usage statistics. This helps us fix bugs and improve features, but the data cannot identify you personally.

How is NUMO different from competitors?

Most competitors don't track Premium Bonds well (we do, brilliantly). Their mortgage calculators are basic. Their UX is stuck in 2012. We've fixed all of this.

Can I use NUMO offline?

Yes! NUMO is offline-first. All calculations happen on your device. You don't need internet for any of the core features.