Comparison

10K Trainer by C25K® vs FlexChallenge

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

10K Trainer by C25K®

This app guides beginners from sedentary to running a 10K in 14 weeks with a structured walk/run program. It features an audio coach, progress tracking, and community support. Ideal for those new to running or graduating from a 5K program.

Highlights
  • 14-week walk/run training plan
  • Audio coach guidance
  • Progress tracking
  • Community forums
  • Integration with Health app
  • Music integration
Features
Read full description

■ The Official 10K Trainer app with millions of success stories! ■ Official partners and the ONLY C25K (Couch to 5K) app featured on FITBIT and SAMSUNG smart watches! ■ Featured on The New York Times, Los Angeles Times, The Washington Post, The Guardian, The Huffington Post, Men's Fitness, Forbes, Mashable, Glamour Magazine, Popsugar Fitness, CBS News, NBC News, Macworld, Cosmopolitan, Lifehacker, WebMD and many more! "Daily programs that alternate between short bursts of walking and running until you're ready to go the distance." - Forbes "One of the highest-rated health and fitness apps... A modest, realistic workout schedule." - Men's Fitness ≈ Real-Life Inspirational Transformations ≈ ◎ Over 175,000 Likes and 1500 Success Photos at facebook.com/c25kfree ◎ Our community inspires one another (and inspires us!) everyday. Hear some of their amazing stories. "In this last year I have lost 97 lbs, gotten off insulin and 9 other medications, completed the C25K running app and started the 10k app. Life is a blessing." - Diana “I went from a size 16 to a size 7. I tell anyone I can about the app. because it was nothing short of a life changer.” - Amber 10K Trainer is the easiest program to get beginners from couch potatoes to 10K distance runners in just 14 weeks. By the same experts who created the #1 C25K® (Couch to 5K) training app! Don’t worry, if you are already a 5K graduate, you can skip ahead and pick up where C25K® app leaves off! This proven 14 week plan will allow users to slowly build strength and stamina by alternating between walking and running. The blend of walking and running together reduces the overall impact and risk of injury, keeps your body guessing, and prepares you to go the distance. By the end of the program, you will be stronger and healthier than you have ever been. You'll be a 10K runner! Turn on our award winning music and just press start! Our audio coach will guide you through your run! It's that easy! ≈ Less is More ≈ ◎ First week free! Easy to learn. Just press start! ◎ Ideal for beginners. ◎ 14 weeks total. ≈ Features ≈ ◉ Easiest 10k program at only 3 times/week ◉ Convenient audio coach and alerts ◉ Map your run at the end of your workout! ◉ Light and dark modes ◉ Integrates with the Health app ◉ Free iPad integration for indoor treadmills ◉ Integrated with Facebook, Twitter, and Instagram ◉ Access to our forums with thousands of veterans and newcomers starting the app. Join the community and meet other runners! ≈ NEW Zen Unlimited Pass - Try it for free! ≈ ◉ Award winning music curated from top DJ's! ◉ Scientifically proven to increase motivation by 35% ◉ Unlimited access to all pro features across ALL Zen Labs Fitness apps ◉ Unlock calories, distance, Apple watch integration, and more ◉ One subscription unlocks all our apps! Questions/comments? Please email us at contactus@zenlabsfitness.com, or visit us at www.zenlabsfitness.com. ≈ Connect ≈ Facebook: @C25Kfree Twitter: @C25Kfree Instagram: @officialc25k Hashtag: #C25K Zen Labs is a proud supporter of the National Breast Cancer Coalition. breastcancerdeadline2020.org Subscription pricing and terms: The subscription will automatically renew unless turned off in your iTunes Account Settings at least 24 hours before current period ends. You can go to your iTunes Account settings to manage your subscription and turn off auto-renew. Your iTunes Account will be charged when the purchase is confirmed. If you subscribe before your free trial ends, the rest of your free trial period will be forfeited as soon as your purchase is confirmed. Privacy Policy & Terms of Use: https://www.zenlabsfitness.com/privacy-policy/ Legal Disclaimer This app and any information given by it or by Zen Labs LLC are for educational purposes only. You should always consult your healthcare provider before beginning any fitness program. C25K® is a registered trademark of Zen Labs LLC

About

FlexChallenge

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Most goals don't fail from lack of motivation. They fail because there's no structure. FlexChallenge gives any goal a start date, an end date, and a daily checklist — then holds you to it. Create a custom challenge for anything: fitness, reading, meditation, learning a skill, breaking a bad habit, or a structured program like 75 Hard. Pick your duration, pick your daily tasks, and show up. YOUR CHALLENGE, YOUR RULES • Any goal, any habit — you define what counts • 7 to 365 days, you set the finish line • Strict mode (miss a day, start over) or flexible mode — your call • Run multiple challenges at once TASK TYPES THAT FIT REAL LIFE • Checkboxes for simple daily habits • Counters for quantities — pages read, reps done, minutes practiced • Timed tasks for focused sessions • Water tracking with one-tap quick add • Automatic step counting via Apple Health SEE YOUR PROGRESS EVERYWHERE • Visual calendar that shows your streak at a glance • Home screen widgets so your challenge stays in front of you • Stats and charts that prove you're changing • Progress photos and voice notes to document the journey • Daily reminders so no day slips by FLEXCHALLENGE PRO Start with a 14-day free trial. Then $24.99/year or $3.99/month, billed through the App Store. Cancel anytime. Terms of Use: https://flexchallenge.app/terms Privacy Policy: https://flexchallenge.app/privacy PRIVATE BY DESIGN No account. No feed. No social pressure. Everything stays on your device — it's just you and your goals. Whether you're building a morning routine, training for something big, or finally finishing what you start: the challenge starts the day you create it. Start today. Stay consistent. Become who you want to be.

Screenshots

10K Trainer by C25K®4 screens
FlexChallenge4 screens

Verdict

The call

The clearest difference is ads: FlexChallenge at none against 10K Trainer by C25K®'s shown. FlexChallenge also leads on update cadence (every 6 days vs every 6 weeks). 10K Trainer by C25K®'s advantage is device support (4 vs 1) and iOS requirement (14.0 vs 17.6). On price and in-app purchases there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. 10K Trainer by C25K® sells 6 in-app purchases, starting at $4.99 per month and FlexChallenge sells 2 in-app purchases, starting at $3.99 per month. Whichever you choose, the download price is not the number that matters.

UpkeepUpdate frequency

10K Trainer by C25K® ships an update every 6 weeks, FlexChallenge every 6 days. The most recent releases landed on November 4, 2026 and October 28, 2026 respectively.

Scorecard4 real differences · 6 level
10K Trainer by C25K® versus FlexChallenge: the parameters behind the verdict, then further details
Parameter10K Trainer by C25K®FlexChallenge
PriceFreeFree
Rating4.8 (22K ratings) — better—
Positive reviews76.3% of reviews—
Number of ratings22K — better—
Update frequencyEvery 6 weeksEvery 6 days — better
AdsYesNo — better
In-app purchasesYesYes
MonetizationFree with in-app purchases—
DevicesiPhone, iPad, iPod, Apple Watch — betteriPhone
Requires iOS14.0 — better17.6
Further details — not scored
Size321 MB17 MB
Age rating4+4+
DeveloperZen LabsLocal Wave Studios LLC

Bugs and requests

10K Trainer by C25K®

Reported bugs

2 issues
  • Timers not syncing accurately with other devices
  • Workout data sometimes not recorded properly

Requested features

3 requests
  • Apple Watch integration for standalone use
  • More advanced training options beyond just 10K
  • Ability to customize audio prompts and volume

FlexChallenge

Not enough reviews yet to summarise bugs or requests.

In-app purchases

6 purchases

10K Trainer by C25K®

Subscriptions4
  • Zen Unlimited Pass Monthly1 Month trial$4.991 Month
  • Unlock Your Potential7 Days trial$29.993 Months
  • Unlock Your Potential1 Month trial$29.993 Months
Show 1 more
  • Zen Unlimited Pass Annual7 Days trial$74.991 Year
One-time2
  • Remove Ads$1.99
  • Go To Pro$6.99
2 purchases

FlexChallenge

Subscriptions2
  • FlexChallenge Pro Monthly14 Days trial$3.991 Month
  • FlexChallenge Pro Yearly14 Days trial$24.991 Year

Questions

Is 10K Trainer by C25K® free?
10K Trainer by C25K® is free to download, with in-app purchases available.
Is FlexChallenge free?
FlexChallenge is free to download, with in-app purchases available.
Do 10K Trainer by C25K® or FlexChallenge have ads?
10K Trainer by C25K® shows ads; FlexChallenge does not.
Which is updated more often, 10K Trainer by C25K® or FlexChallenge?
10K Trainer by C25K® ships an update every 6 weeks, and FlexChallenge every 6 days. Most recently, 10K Trainer by C25K® was updated on November 4, 2026 and FlexChallenge on October 28, 2026.

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