RideMath (hjmtjf.com) is a small set of free tools that turn "work it out by hand again, then go looking it up again" into "fill in a few boxes, press one button". The site currently holds 20 tools. The site is about: Calculators that answer questions you actually ask on the bike. Everything runs in your browser: no sign-up, no login, nothing you type is uploaded.
Who it is for
Three groups, mostly. First, people who already have the numbers and simply do not want to re-key them into a calculator every time - someone drafting a budget, or an operator who needs a rough figure to align with a colleague in the next ten minutes. Second, people preparing for an exam, an interview, an application, or a document they have to submit, who want a way to test "what if I change this number". Third, teachers, coaches, and leads who need to explain a rule of thumb rather than hand over an answer.
Whatever group you are in, the position of this site is the same: it puts the reasoning in front of you instead of making the decision for you.What a tool returns is a reference value computed from the inputs you supplied. Before you act on it, you still check it against the source material, the situation on the ground, or the official guidance.
How the tools are built
Every tool has an explicit, reproducible method: what goes in, what formula is applied, what comes out. The logic is not hidden - the full calculation is visible in the page source. That buys two things. The result can be checked by somebody else, and if you think a number is wrong you can follow the formula to the step whose assumption does not hold, instead of choosing between trusting it and not trusting it.
Because all of it runs locally, the amounts, durations and ratios you type never leave the device. That matters most for the inputs that describe your own situation.
How the content is held to a standard
Every page has a floor it has to clear: enough body copy that it is not just a form with a button; at least four questions answered, with the three things that actually decide whether a tool is used well written down - how to use it, where people go wrong, and when it does not apply. Where a page states a specific number, a price, a fee or a rule, it says "check the official source" and gives you a route to check it yourself, rather than inventing a number that looks plausible.
Instructions, the verdict labels and the computed result are kept separate. Instructions tell you how to use the tool, the labels qualify what the number means, and the result is the number. Mixing those three is how a conclusion drawn under one set of conditions quietly turns into a general rule, and it is a mistake we keep going back and fixing.
What this site does not do
It does not give medical diagnoses, medication doses, legal opinions or investment advice. The tools help you frame a question better or get the arithmetic right; the conclusion still comes from a qualified professional or from the official source. For outdoor, diving, wildlife, protected-area and border situations, the site provides safety checklists and official contacts only - it does not provide decompression tables, does not certify any depth or weather as safe, and does not explain how to work around regulations.
What changes over time
Tool pages get reviewed: does the logic still hold, is the reference data still current, are the stated limits still true. When the premises of a tool change, the wording on the page changes too, rather than leaving a stale conclusion in place. If a page does not match what you are seeing in practice, the contact details in the footer are the way to tell us.
What is on the site
- Bike Fit Estimator - Frame size, stack, reach and saddle height from body measurements and flexibility — with a comparison to popul
- Brake Distance Calculator - Reaction + braking distance for rim vs disc brakes, dry/wet/leafy conditions, downhill, with a stop-distance l
- Cadence & Muscle Efficiency - Find your self-selected cadence sweet spot from duration, intensity, and training goals.
- Bike vs Car Carbon Footprint - Compare cycling vs driving, transit, or walking on a per-km carbon basis — including your food calories and gr
- CdA / Aero Time Saver - Compare aerodynamic drag between positions, helmets and wheels, see the actual seconds saved at race speed, in
- Chain Wear & Replace Timing - Predict remaining chain life based on mileage, riding conditions, drivetrain cost, and stress factors.
- Climb Difficulty Grader - Beyond the Cat 1-4 scale — get a realistic time estimate from your W/kg and the climb's gradient profile, with
- Crank Length Recommender - Crank length from inseam, hip mobility, and discipline. Not the generic 172.5 mm-for-everyone answer.
- E-Bike Range Estimator - Realistic e-bike battery range across assist levels, terrain, temperature, and rider effort.
- Fueling Plan Generator - Carb and caffeine minute-by-minute plan for long rides and races, with gut-training notes.
- FTP Zones & Race Pace Calculator - 7-zone training model plus race-specific pacing targets for road, gravel, criterium and time-trial.
- Gear Ratio Visualizer - See all your gears as a speed-vs-cadence grid, find dead-spot gears, ideal cruising ratios, and step size betw
- Hydration & Sodium Planner - Hour-by-hour fluid and electrolyte plan from temperature, humidity, wind, and intensity.
- Bikepacking Weight Budget - Day-by-day weight and resupply planning for multi-day tours — including packed food and water targets.
- Spoke Tension Checker - Predict target spoke tension from rim, tire, wheel spec, riding style, and weight — with a tolerance band for
- Segment Time Predictor - Predict climb and time-trial segment times from FTP, weight, and conditions. Compare to KOM, top 10%, and your
- Tire Pressure Optimizer - Get a target tire pressure plus upper/lower bounds from system weight, tire width, surface, and tubeless vs tu
- Watts / kg & Climb Time Predictor - Calculate watts per kilogram, FTP category, and realistic climb times for 5%, 8% and 10% gradients — including
- Ride / No-Ride Weather Decider - Forecast input → go/no-go decision + risk checklist (wind, ice, lightning, visibility).
- Ride Comfort Index - Wind chill + WBGT + clothing recommendations for the bike, including frostbite and heat-stress warning zones.
Questions
Do the tools need an account or a payment?
No. Every tool on RideMath is free, needs no account, and works before you type anything personal. The numbers you enter are used by the calculation on the current page and are gone when you reload.
Can I treat the output as a final answer?
Not on its own. A tool returns a magnitude under the conditions you typed in. It does not include what it costs to act, what might change while you act, or how the other side behaves. Before spending money, signing, or promising something to a third party, check the result against the source material and the official position.
What is the most reliable way to use these tools?
Follow the order given in the usage section: get your figures onto the same basis first, fill in one field at a time, then calculate. Checking that every unit matches the thing you are actually measuring catches more wrong answers than any other habit, and it takes about ten seconds.
My number does not match what I expected. What should I check?
Three things: that the units agree, that you have not left an optional field blank and accepted its default, and that you recalculated after editing an input. If all three are fine, the likely explanation is that your basis differs from the one the tool assumes - the limitations section on each tool page says what it covers.
Will the pages stay available?
We try to keep them, but the premises of a tool, the reference data and the outside world all move. Pages get reviewed and corrected as that happens. If you need to keep a result long term, take a screenshot and record the inputs you used.