Methodology & sources

The finder maps a weight to the adult IBJJF gi divisions. The defining detail is that IBJJF weigh-ins are conducted with the athlete in the full gi, so the published division caps are gi-on weights, not bodyweight. We store the male and female adult division limits and return the lightest division whose cap the entered weight does not exceed.

Kilogram limits are treated as authoritative; pound figures are the IBJJF-published equivalents. We intentionally do not provide no-gi limits in this tool, because no-gi divisions use different caps (no kimono on the scale) and mixing them is exactly how people show up to the wrong bracket.

The planner takes current weight, target weight and days remaining, computes the total loss required and expresses it as a percentage of bodyweight lost per week. It then classifies the plan: at or below roughly 1% of bodyweight per week is treated as a sustainable range; 1–1.5% as aggressive; above 1.5% as high risk. This framing follows sports-nutrition guidance that gradual loss preserves performance and health, while rapid cuts — especially acute dehydration — carry real danger.

The tool deliberately avoids prescribing aggressive dehydration protocols. It is a safety planner that nudges toward gradual loss or competing a division up, not a crash-cut generator.

Scoring follows the IBJJF points system: takedown 2, sweep 2, knee-on-belly 2, guard pass 3, mount 4, back control with hooks 4. A submission ends the match. Each scoring position requires roughly three seconds of stabilised control to count. When time expires, points decide the match; ties break to advantages, then penalties, then referee decision. The calculator tracks all of these per athlete.

IBJJF age divisions are determined by the age an athlete reaches during the competition year, calculated as competition year minus birth year — not age on the day of the event. The tool applies this rule to place a birth year into Juvenile 1–2, Adult, or Master 1–7. Athletes may compete down (into Adult) but not up into an older Master bracket than their age permits.

The finder maps height and weight to a starting A-size (A0–A5, with F-sizes noted for women). Because there is no universal A-size standard — each brand publishes its own measurements — the result is explicitly a starting point to confirm against the manufacturer’s chart, with guidance on how shrinkage and build shift the choice. We do not claim a single ‘correct’ size across brands.

The estimate is driven by fabric type, wash temperature and drying method, reflecting that cotton contracts with heat — most in hot wash plus hot tumble-dry, least in cold wash and hang-dry — while pre-shrunk and ripstop fabrics move far less. Because real shrinkage depends on the specific gi, prior washing and exact blend, the output is presented as a directional guide for how to wash, not a precise final measurement.

Resting metabolic rate is estimated with the Mifflin–St Jeor equation, the best-validated of the common predictive formulas. It is multiplied by an activity factor scaled to weekly training frequency, then adjusted modestly for the stated goal (maintain, lean, gain). Macros default to roughly 2 g protein per kg bodyweight, ~25% of calories from fat, and the remainder from carbohydrate, with a sensible calorie floor. These are evidence-aligned defaults, not a personalised prescription — a registered sports dietitian should be consulted for individual plans.

The estimator anchors on IBJJF graduation system minimums — about 2 years at blue before purple, 1.5 years at purple before brown, and 1 year at brown before black, with no fixed minimum from white to blue — then layers typical progression rates by training frequency to produce a range. It is explicit that promotion is the instructor’s decision and that the minimums are floors, not expected timelines.

This tool presents general return-to-sport timeframes by injury type and severity, drawn from published sports-medicine ranges. It is educational only and explicitly not medical advice; it flags injuries that require professional management (concussion, post-surgical recovery) and conditions that mandate staying off the mat entirely until cleared (skin infections such as ringworm, staph and herpes gladiatorum). Any output is a starting point for a conversation with a qualified clinician.

The read estimates weekly training stress from session count and intensity, then compares it to a recovery capacity shaped primarily by sleep and modulated by age, returning a simple recovered / balanced / monitor / back-off judgment. It draws on the established training-stress-versus-recovery framework underpinning load monitoring in sport. It is a directional guide based on those principles, not a validated clinical instrument.