About PaceCalculator.online

This site is built and run by one person: me, David Greenwood, an IT manager with a background in web development — and a runner — based in North Yorkshire, England. Every calculator, chart and pace band on this site exists because at some point during five years of training and racing, I needed it and couldn't find a version I liked.

Who I am

I'm an IT manager by trade, a web developer by background, and a runner by stubbornness. I want to be straight with you from the start: I am not a running coach and I hold no coaching qualifications. What I am is an ordinary, mid-pack — honestly, often back-of-the-pack — runner who spent five years training on quiet Yorkshire lanes, raced everything from a 10K to the London Marathon, and did all of the pace maths the hard way: on paper, the night before races. This site is my old trade applied to my sport.

My running

I started racing in 2015 with the Leeds 10K and the Leeds Half Marathon, came back for the Leeds Half again the next spring, then stepped up to the marathon at York — twice, in 2016 and 2017 — before getting a place in the 2018 London Marathon.

London 2018 turned out to be the hottest London Marathon on record at the time, with temperatures around 24 °C. But what surprised me most wasn't the heat — it was the noise. I did nearly all of my training alone on rural Yorkshire roads, where the loudest thing you'll hear is a tractor or the odd startled pheasant. The wall of sound in London was relentless from the first mile. Near the end, when I had nothing left, that crowd noise genuinely carried me. But I'll also admit something every honest marathoner will recognise: when the course dipped into an underpass where no spectators could stand, the sudden quiet was such a relief that I walked through it — and I'd do it again.

I'm not currently running. Life got in the way, as it does. I'm hoping to find my way back to the start line, and building this site — thinking hard about pacing, splits and race plans again — is part of that.

Race history

These are my real results. There isn't a fast time among them, and that's rather the point: this site is built by someone who has done his pacing maths from the middle and the back of the pack, where a realistic plan matters most.

The London time is my official chip time (bib 52590, category 18–39), run in record heat.

Running for the YMCA

My London Marathon place came with a fundraising commitment to YMCA England and Wales — the largest provider of safe, supported accommodation for young people in England and Wales. Raising the money was honestly as much of a challenge as the training. I took part in the YMCA's Sleep Easy sleep-out to get a small taste of what a night without a home feels like, and we ran a Movies & Music charity quiz night at the Bay Horse Inn.

I didn't do it alone. My good friend James, Chairman of Ripon YMCA, was a huge source of encouragement throughout, and my wife Claire put an enormous amount of work into the fundraising events. Together we raised £2,330.50 against a £2,000 target — the JustGiving page is still online if you'd like to see it.

What this site believes

• Free means free. No sign-up, no account, no paywall.
• Private by design. Every calculation runs in your browser — nothing you type is sent anywhere.
• Numbers you can check. Pace is just time divided by distance. Every formula this site uses is explained on the page, so you can verify any result by hand.
• Built for real runners. Tools that work at 6 am in a race-morning portaloo queue: fast, simple, readable on a phone.

Accuracy & disclaimer

The calculators are accurate for the arithmetic they perform. Race-time predictions based on a single pace are estimates only — real performance depends on terrain, weather, fitness and pacing. Use the results for planning and motivation, and consult a qualified coach or medical professional for personalised training or health advice.

Get in touch

Suggestions or found a bug? Email hello@pacecalculator.online — I read every message.