Kuro Lab
Running Pace Calculator
Tools / Calculators
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Running Pace Calculator

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Enter your current weight and finish time to see your predicted running record and pace as your weight changes.

Method

% weight lost ≈ % time improvement

Weight

Current record

Predicted record

50:00

Current record (5:00 /km)

47:51

Predicted record (4:47 /km)

With a 4.3% weight loss, expect about 2:09 faster

Predicted record by weight loss (1–10kg)

LossTarget weightPredicted recordPaceTime saved
-1kg69.0kg49:174:56 /km-0:43
-2kg68.0kg48:344:51 /km-1:26
-3kg67.0kg47:514:47 /km-2:09
-4kg66.0kg47:094:43 /km-2:51
-5kg65.0kg46:264:39 /km-3:34
-6kg64.0kg45:434:34 /km-4:17
-7kg63.0kg45:004:30 /km-5:00
-8kg62.0kg44:174:26 /km-5:43
-9kg61.0kg43:344:21 /km-6:26
-10kg60.0kg42:514:17 /km-7:09

⚠ marks a range where the weight change exceeds 5%, so the margin of error grows

How to use

1

Choose a method: the 1% rule or the Jack Daniels formula.

2

Enter your current and target weight, plus your distance and finish time.

3

See your predicted record and pace, along with a table of scenarios for losing 1–10kg.

자주 묻는 질문

Q1. What's the difference between the 1% rule and the Jack Daniels formula?

The 1% rule simply assumes your time improves by the same percentage as your weight loss. The Jack Daniels formula is based on real runner data and calculates a larger time savings per kg as distance increases, making it more precise.

Q2. Does losing weight really make you faster?

Generally yes, but the actual effect depends on how the weight is lost (muscle loss vs. fat loss) and your fitness level. This calculator gives an estimate based on the statistical relationship between weight and pace.

Q3. Why does accuracy drop for large weight changes?

When weight changes by more than about 5%, factors the formulas don't account for — muscle loss, fitness changes, metabolism — have a bigger effect, so the actual result can diverge from the estimate.

Q4. Is my weight or record saved anywhere?

No. All calculations happen entirely in your browser and are never sent to or stored on a server.

Q5. Can I calculate distances other than 5K or 10K?

Yes. Select "Custom" in the distance dropdown to enter any distance in kilometers.

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