# Tick Data and OHLCV Data

> Tick data records every trade or quote; OHLCV bars summarise them by time. Learn how bars are built, other bar types, storage costs and which data a strategy needs.

Source: https://learn.tradelabsai.com/programming/tick-data-and-ohlcv-data/  
Track: Programming and Data · Level: Intermediate · Updated: 2026-10-03  
Publisher: TradeLabs AI (https://tradelabsai.com). Education, not financial advice.  
Cite as: TradeLabs Learn, "Tick Data and OHLCV Data", https://learn.tradelabsai.com/programming/tick-data-and-ohlcv-data/

Market data comes at different resolutions. Tick data records every individual trade, and sometimes every quote change, exactly as it happened. OHLCV bars summarise those ticks into fixed periods: the open, high, low and close prices plus volume for each minute, hour or day. Bars are compact and easy to work with, which is why most charts and backtests use them. Ticks preserve details that bars throw away, such as the order in which highs and lows happened. Choosing the right resolution affects both the cost of research and whether its results can be trusted.

## What each contains

| | Tick data | OHLCV bars |
|---|---|---|
| Content | Each trade (time, price, size), and for quote data each bid and ask change | Open, high, low, close and volume per period |
| Size | Very large | Much smaller |
| Detail | Full sequence of events | Summary per period |
| Best for | Execution research, high frequency, precise fills | Most indicators, swing and position strategies |

## How a bar is built

For each period, take all trades inside it:

- **Open:** price of the first trade.
- **High:** highest trade price.
- **Low:** lowest trade price.
- **Close:** price of the last trade.
- **Volume:** sum of trade sizes.

This is exactly what a candlestick shows. See [How to Read Candlesticks](https://learn.tradelabsai.com/candlesticks/how-to-read-candlesticks/).

**Example: Building a one minute bar**
Between 10:00:00 and 10:00:59, five trades occur at $50.10 (200 shares), $50.15 (100), $50.05 (300), $50.20 (150) and $50.12 (250). The one minute bar is open $50.10, high $50.20, low $50.05, close $50.12 and volume 1,000 shares. The bar does not show that price dipped to the low before reaching the high. A strategy with a stop at $50.06 and a target at $50.19 cannot tell from the bar alone which was hit first; the ticks show the stop came first. See [Fill Models, Partial Fills and Order Queues](https://learn.tradelabsai.com/research/fill-models/).

## Bar labelling: start or end?

Some vendors label a bar with its start time (10:00 for 10:00 to 10:01); others use the end time. If you treat a start labelled bar as complete at its label time, your backtest sees its close a full bar early. Always check the convention. See [Timestamps, Time Zones and Daylight Saving](https://learn.tradelabsai.com/programming/timestamps-and-time-zones/) and [Look-Ahead Bias](https://learn.tradelabsai.com/research/look-ahead-bias/).

## Other bar types

| Bar type | New bar forms when | Why use it |
|---|---|---|
| Time bars | A fixed time passes | Standard and simple |
| Tick bars | A set number of trades occur | More bars in active periods |
| Volume bars | A set volume trades | Normalises activity |
| Dollar bars | A set value trades | Comparable across price changes |
| Range and Renko bars | Price moves a set amount | Focus on movement, not time |

Some researchers argue that volume and dollar bars produce returns with better statistical properties than time bars, since they sample more during busy periods.

## Storage costs

Tick data can be hundreds or thousands of times larger than minute bars. A liquid futures contract can print hundreds of thousands of trades in a busy day, and quote data is larger still. Columnar formats and compression help a lot. See [Data Storage, Compression and Caching](https://learn.tradelabsai.com/programming/data-storage/).

## Which data do you need?

| Strategy | Minimum data |
|---|---|
| Long term investing, monthly rebalancing | Daily bars |
| Swing trading | Daily or hourly bars. See [Swing Trading](https://learn.tradelabsai.com/strategies/swing-trading/) |
| Intraday trading with stops and targets | Minute bars, with tick checks on fill sensitive rules |
| Scalping and market making | Tick and quote data. See [Scalping](https://learn.tradelabsai.com/strategies/scalping/) |
| Execution research | Trades and quotes with precise timestamps |

## Quotes versus trades

Trade prices tell you what happened; quotes tell you what you could have traded at. A backtest using last trade prices for entries ignores the spread. For short term strategies, use bid and ask data to model buying at the ask and selling at the bid. See [Bid-Ask Spread](https://learn.tradelabsai.com/markets/bid-ask-spread/) and [Spread Costs](https://learn.tradelabsai.com/orders/spread-costs/).

## Frequently asked questions

### What is tick data?

A record of every individual trade, and sometimes every quote change, with its time, price and size.

### What does OHLCV stand for?

Open, high, low, close and volume, the summary values of a price bar.

### Do I need tick data for backtesting?

Not for most daily or hourly strategies. Short term strategies with tight stops and targets, or that depend on the spread, benefit from tick and quote data.

Next, learn how live data reaches your system in [Real-Time, Delayed and Historical Data](https://learn.tradelabsai.com/programming/real-time-data/).

## Continue learning

- Next lesson: [Real-Time, Delayed and Historical Data](https://learn.tradelabsai.com/programming/real-time-data/)
- Previous lesson: [Market Data Levels: Level 1, 2 and 3](https://learn.tradelabsai.com/programming/level-2-data/)
- Related: [Market Data Levels: Level 1, 2 and 3](https://learn.tradelabsai.com/programming/level-2-data/): Level 2 data shows bids and offers at multiple prices beyond the best quote. Learn level 1, 2 and 3 data, how to read depth, its limits and how traders use it.
- Related: [How to Read Candlesticks](https://learn.tradelabsai.com/candlesticks/how-to-read-candlesticks/): Learn to read candlestick charts: open, high, low and close, bodies and wicks, timeframes, and what a candle tells you about buyers and sellers.
- Related: [Historical Data for Backtesting](https://learn.tradelabsai.com/research/historical-data-for-backtesting/): Backtests are only as good as their data. Learn data types and sources, quality checks, corporate action adjustments and how to avoid survivorship traps.
- Related: [Data Storage, Compression and Caching](https://learn.tradelabsai.com/programming/data-storage/): Compare ways to store market data: CSV, Parquet, HDF5, PostgreSQL, time series and columnar databases. Learn compression, partitioning and how to choose.
- Related: [Timestamps, Time Zones and Daylight Saving](https://learn.tradelabsai.com/programming/timestamps-and-time-zones/): Time zone and timestamp errors silently break backtests. Learn UTC storage, daylight saving traps, exchange sessions, event versus receive time and bar labels.
- Related: [Market Data Explained](https://learn.tradelabsai.com/alternative-data/market-data-explained/): Market data covers trades, quotes, order book depth and reference data. Learn the main types, levels of data, real time vs delayed feeds, costs and common pitfalls.