| What it does | Free online calculators, converters, and developer tools that run in your browser
| Free Karvonen formula heart rate zone calculator
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| Stage | Startup
| Established
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| Founded | 2025
| Not given
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| Based in | Not given
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| Pricing model | Free
| Free
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| Pricing | Not given
| Not given
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| Key features | - 68 free tools across finance, development, and utilities
- Loan repayment and affordability calculators with total interest calculations
- Currency converter with 30 world currencies and live exchange rates
- JSON formatter, validator, and minifier with syntax highlighting
- Date and time tools including age calculator and timezone converter
- Runs entirely in browser with no server uploads
- Works offline after initial page load
| - Five personalized training zones based on heart rate reserve
- Accounts for resting heart rate and cardiovascular fitness
- Custom maximum heart rate input from multiple formulas
- No signup required, runs entirely in browser
- Weekly resting heart rate logging and progress tracking
- Zone-specific training guidance for different goals
- Shareable and printable zone results
- Embeddable calculator widget for websites
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| What makes it different | - No account or sign-up required
- Runs entirely client-side in your browser with no data sent to servers
- All tools are completely free with no usage limits
- Works offline after initial page load
- Privacy-first approach with no data collection or transmission
| - More accurate than age-only formulas, accounting for individual cardiovascular fitness
- Zones adapt as your fitness improves and resting heart rate drops
- Based on 1957 Karvonen research used by coaches and sports scientists
- Independent, no data collection or external servers
- No ads inside the calculator, free to use with optional embedding
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| Community votes | 0 | 0 |
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| DR (Domain Rating by Ahrefs) | 4 ● no change since last check | 11 ● no change since last check |
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| Trust Flow (Majestic) | 3 | 19 |
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| Citation Flow (Majestic) | 35 | 25 |
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| Referring domains (Majestic) | 6 | 40 |
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PlayTools
CalculateMyHeartRate