Yamato Body Planner™ DF870

BODY COMPOSITION

Evidence-based BIA analysis · Yamato-calibrated classifications

Frequently Asked Questions

About JOIFIT24 DF870, the Yamato body scanner, and how it works

What is JOIFIT24 DF870?
JOIFIT24 DF870 is a free, unofficial body composition tracker built for the Yamato DF870 body scanner (体組成計) found at JoyFit24 (ジョイフィット24) gyms in Japan. It reads QR codes from the DF870 scale, analyzes your body composition data with evidence-based classifications, and tracks your progression over time with detailed charts and coaching.
Who developed this?
JOIFIT24 DF870 was developed by Marco Martinelli as a personal, non-profit project. It started as a simple tool to track body scans and evolved into a full body composition platform with health analytics, blood test tracking, coaching, and more. It is not affiliated with JoyFit Co., Ltd. or Yamato Scale Co., Ltd.
What is the Yamato DF870?
The Yamato DF870 (Body Planner DF870) is a professional body composition analyzer manufactured by Yamato Scale Co., Ltd. It uses bioelectrical impedance analysis (BIA) to measure weight, body fat %, muscle mass, visceral fat, bone mass, body water, BMR, and segmental data for arms and legs. These scales are commonly found at JoyFit24 gyms across Japan.
Where can I find a Yamato DF870?
Yamato DF870 analyzers are available at JoyFit24 gyms throughout Japan. For home or commercial use, contact Yamato Scale Co. directly.
Is it free?
Yes, completely free. No subscriptions, no ads, no hidden costs. All features — QR scanning, body composition analysis, progression charts, health analytics, blood test tracking, coaching, and Excel export — are available at no charge.
How do I create an account?
JOIFIT24 DF870 is currently in closed testing. New registrations are temporarily disabled while the platform is being refined. If you'd like to request access, send an email to marco.martinelli.85[at]gmail.com with your name and a brief reason for your interest.
You can still try the app without an account — scan or paste a QR code on the home page, or log in with the demo account to explore all features.
What metrics does it track?
From the scanner: weight, BMI, body fat %, visceral fat index, muscle mass, skeletal muscle index (SMI), fat-free mass index (FFMI), waist-to-height ratio (WHtR), basal metabolic rate (BMR), bone mass, body water %, and segmental muscle/fat data for arms and legs.
Health modules: manual body measurements (chest, waist, hips, arms, legs, neck), blood test tracking with computed indices (HOMA-IR, TG/HDL, AIP, CRI, T:C ratio, Navy BF%), and progress photos.
How accurate is BIA (bioelectrical impedance)?
BIA provides accuracy of approximately ±2-3% for body fat percentage. For best results: measure fasted (or 2+ hours post-meal), well-hydrated, at the same time of day, after voiding, and avoid exercise 12 hours before. Consistency in measurement conditions matters more than absolute accuracy when tracking trends over time.
Is this medical advice?
No. JOIFIT24 DF870 is for informational and educational purposes only. It is not a medical device and does not provide medical advice. Body composition data from BIA is an estimate. Always consult healthcare professionals for medical decisions.
JOIFIT24 DF870 — developed by Marco Martinelli. Free, non-profit, unofficial. Not affiliated with JoyFit or Yamato Scale Co. For professional fitness guidance, visit joyfit.jp.