Spark & Anvil Privacy
Lane Four, SplitForge’s pool — Marlin the coach on the deck beside the starting blocks, two young swimmers in the lanes and a big pace clock on the wall

🏁 Ages 9–14 · Ratio & Percent

SplitForge

Your times are the maths. Enter your own swim, run, or bike times and learn pace, percent improvement, splits, conversions, and qualifying cuts straight from the clock — with five little coaches who each teach one move.

🏊 Log a time 🏅 Race the meet
The same pool-deck maths at every age. From counting lengths at 3 to reading the points curve at 18, and a course for grown-ups. See the ladder →

Start here

The lane Log your OWN times, guess your improvement first, then race your ghost. Best, average and % — each with how many swims it comes from. The meet A meet built from your own times — every coach’s move, three different ways. The pace clock Read the pool clock, work out send-offs, and try to hold a pace. Together Build a relay with the people in the room, or work out a class’s field-day numbers. Cut & Convert Turn your gap to a cut into a pace per 50, and convert yards to metres two honest ways. Deck mode For a grown-up on the pool deck: type the digits off the board, one hand. The stopwatch Time something real — and find out why a hand time is faster than the true time. My season book Your season on one page, ready to print. Teach the coaches Four coaches are still learning their move. Catch their slip and teach them — you learn it best. Percent Bot A bot that is right on hard ones and wrong on easy ones. Checking it is always the smart move. Seed the heats Fastest swimmers last, fastest of each heat in lane 4 — guess first, then seed.

Meet your coaches

Marlin runs Lane Four. He reads the pace clock with you and introduces the five little coaches below — each one is one part of the ratio-&-percent maths. Marlin is not an AI — SplitForge has no AI at all. Every number is worked out by the app’s own maths engine, right on your device.

  • Split the Stopwatch — mixed-unit subtraction — the take-away between two clocks
  • Pace the Penguin — the unit rate — your time shared out over every 100m
  • Cut the Standard-Setter — the inequality — your time must be ≤ the qualifying cut
  • Convert the Otter — yards ↔ metres — a yard is a little shorter than a metre
  • Taper the Tortoise — the season graph — your best, your average, your improvement

🔒 SplitForge runs right here on your device. Your times are personal — they stay on THIS device only. There is no account, no ads, and no AI, and nothing you enter is sent anywhere.

Cast, stories & more

More ways to play

Deck mode Cut & Convert Stopwatch My season book Percent Bot Seed the heats Teach the Coaches The Hundredths The Star Century of Fast The Hidden Base Pool-deck ladder Lane staggers Fast or clean? A line of classes Write your own rate problem Six against five
SplitForge mascot

Meet the cast — the characters who teach this

Each one stands for an idea you’ll practice. Tap a character to read their illustrated story.

Explore all the stories →

What next? Pick a door

Chosen from what this app is about. What you open is remembered on this device only.